8  I  • 


HOOVER  STEEL  BALL  Co 

ANN  ARBOR,  MICHIGAN 


MANUFACTURERS    OF 


B-A-L-L-S 

STEEL,  BRONZE,  BRASS 
COPPER,  ALUMINUM 

AND  OTHER  MATERIALS  IN  BOTH 
HIGH  AND  COMMERCIAL  GRADES 


MADE   IN  AMERICA 


TO  THOSE  WHO  ARE  INTERESTED  IN  OUR  PRODUCT  WE  WILL, 
UPON  APPLICATION,  GLADLY  FORWARD  OUR  REGULAR  CATALOG 
AND  PRICE  LIST,  GIVING  THE  TRADE  NAME  OF  OUR  DIFFERENT 
GRADES  OF  BALLS,  GUARANTEED  ACCURACY  AND  QUALITY, 
PRICES  AND  TERMS 


TJ/07/ 


FOREWORD 


WE    TAKE    PLEASURE    IN    PRESENTING 
THIS    TREATISE    ON    THE    MANUFAC- 
TURE   OF    STEEL    BALLS    AND    WISH 
TO  THANK  THOSE  WHO  HAVE  SUPPORTED 
US    IN    SUCCESSFULLY    OVERCOMING    THE 
PREJUDICE     AT     ONE     TIME     EXISTING 
AGAINST    AMERICAN    MADE    BALLS. 

THIS  SUCCESS  HAS  BEEN  DUE  TO  THE 
QUALITY  OF  OUR  PRODUCT  COMBINED 
WITH  EXPERT  KNOWLEDGE  OF  THE 
REQUIREMENTS  OF  OUR  CUSTOMERS. 

IN  THE  FOLLOWING  PAGES  WE  HAVE 
ENDEAVORED  TO  SHOW  STEP  BY  STEP 
THE  VARIOUS  STAGES  THROUGH  WHICH 
A  BALL  PASSES  FROM  THE  ROUGH  STEEL 
BLANK  TO  THE  MIRROR -LIKE  FINISHED 
SPHERE. 

THE  OBJECT  OF  THIS  TREATISE  IS  TO 
LAY  BARE  FACTS  WHICH  HAVE  HITHERTO 
BEEN  GENERALLY  UNKNOWN  AND  IF  WE 
SUCCEED  IN  STIMULATING  FURTHER 
INTEREST  IN  THE  BALL  INDUSTRY,  THIS 
WORK  WILL  NOT  HAVE  BEEN  IN  VAIN. 


HOOVER  STEEL  BALL  Co. 

ANN  ARBOR,  MICHIGAN 


372827 


L.  J.   HOOVER 

PRESIDENT    AND    GENERAL    MANAGER 


COMMITTEE    OF   THREE    HAVING    ENTIRE    CHARGE    OF    FACTORY 
MANAGEMENT   AND    MANUFACTURING 


•  »»      *•»  * 


•M  »•    »  • 


hi  0} 

\-  " 

(fl  ,_ 

cr  z 

u  < 

>  -i 

O  a- 

0  H 

1  Z 


Manufacture  of  Steel  Balls 


DURING  recent  years  the  application  of  ball 
bearings  in  machine  design  has  increased  rapidly, 
and  this  type  of  bearing  is  now  used  in  many 
machines  where  plain  bearings  were  formerly 
considered  good  enough.  Until  German  export 
facilities  were  shut  off  by  the  war,  the  majority  of  the 
steel  balls  used  in  these  bearings  were  made  by  the  Deutsche 
Waffen  und  Munitions  Fabriken  of  Berlin,  Germany,  and 
the  product  of  this  firm  has  become  so  celebrated  that  many 
persons  think  the  steel  ball  industry  was  developed  by  the 
Germans.  As  a  matter  of  fact,  the  art  of  ball  making  goes  back 
to  a  very  early  date,  and  the  development  of  original  methods 
for  doing  this  work  is  attributed  to  the  Chinese.  To  those  who 
have  credited  the  Germans  with  the  development  of  commercial 
methods  of  ball  manufacture,  it  will  doubtless  be  of  interest  to 
learn  that  the  first  commercial  steel  balls  were  made  in  this 
country  under  basic  patents  granted  to  Richardson  of  the 
Waltham  Emery  Wheel  Co.,  Waltham,  Mass.,  and  that  the 
original  ball  making  machinery  for  the  plant  of  the  Deutsche 
Waffen  und  Munitions  Fabriken  was  designed  and  built  in  the 
United  States  and  shipped  to  Germany  ready  for  use.  This 
will  be  explained  in  detail  in  connection  with  the  following 
historical  outline  of  important  epochs  in  the  steel  ball  industry. 

HOW  THE  STEEL  BALL  INDUSTRY 
CAME  INTO  EXISTENCE 

IT  HAS  been  stated  that  basic  patents  for  dry  grinders  used 
in  roughing  out  ball  blanks  to  a  spherical  form  were  granted 
to  Richardson  of  the  Waltham  Emery  Wheel  Co.,  in  1887. 
These   patent  rights  were  subsequently  sold   to  the  Cleveland 
Machine   Screw   Co.,    Cleveland,    Ohio,   which   had   control   of 
patents  on  ball  making  machinery  taken  out  by  John  J.  Grant. 
One  of  the  first  firms  to  manufacture  steel  balls  on  a  commer- 
cial basis  was  the  Simonds  Rolling  Machine  Co.,  of  Fitchburg, 
Mass.,  and  the  Fitchburg  Steel  Ball  Co.  was  subsquently  formed 
by  employes  who  left  the  Simonds  firm.     After  a  brief  career, 


the  latter  firm  was  taken  over  by  the  Cleveland  Machine  Screw 
Co.,  and  with  facilities  acquired  through  its  own  development 
work  and  purchase  from  other  companies,  it  was  in  a  position 
to  manufacture  the  majority  of  balls  used  in  the  bicycle  trade. 
In  this  connection  it  will  be  of  interest  to  note  that  up  to  the 
year  1899  balls  one-half  inch  in  diameter  were  the  largest  size 
that  were  manufactured  in  quantities. 

About  1890  the  Cleveland  Machine  Screw  Co.  designed  and 
built  for  the  Deutsche  Waffen  und  Munitions  Fabriken,  of 
Berlin,  Germany,  equipment  used  in  its  original  steel  ball  plant 
and  this  marked  a  most  important  step  in  the  trade,  owing 
to  the  reputation  for  making  high-grade  balls  that  was  later 
acquired  by  this  firm.  The  machines  built  and  shipped  to 
Germany  had  no  reference  to  American  manufacturing  rights, 
and  the  Cleveland  Machine  Screw  Co.  continued  to  operate  its 
plant  in  the  usual  way. 

In  1894  when  a  consolidation  of  bicycle  manufacturers  was 
effected,  the  Cleveland  Machine  Screw  Co.  was  sold  to  the  Pope 
Mfg.  Co.  of  Hartford,  Conn.,  which  at  that  time  started  to 
manufacture  its  own  balls  for  use  in  bicycle  bearings.  The 
requirements  of  balls  for  the  bicycle  trade  were  not  nearly  as 
severe  as  the  standards  which  must  be  met  by  balls  used  in 
high-grade  annular  bearings  at  the  present  time.  This  was 
largely  due  to  the  fact  that  the  cup  and  cone  form  of  races  was 
employed,  allowing  compensation  to  be  made,  and  while  this 
form  of  race  did  not  enable  ball  bearings  to  be  operated  under 
the  most  efficient  conditions,  it  was  the  means  of  overcoming 
discrepancies  due  to  inaccuracies  in  the  size  of  the  balls.  Up 
to  this  time  there  had  been  six  or  seven  firms  engaged  in  the 
manufacture  of  steel  balls,  but  with  the  decline  of  the  bicycle 
industry  a  number  failed. 

In  1901  the  Standard  Roller  Bearing  Co.,  Philadelphia, 
Pa.,  acquired  all  obsolete  and  existing  plants  engaged  in  the 
manufacture  of  steel  balls.  L.  J.  Hoover,  who  was  formerly 
in  the  employ  of  the  Standard  Roller  Bearing  Co.,  left  that  firm 
in  1906  and  formed  the  Grant  &  Hoover  Co.  at  Merchantville, 
N.  J.  The  name  of  this  firm  was  later  changed  to  Atlas  Ball 
Co.,  and  the  plant  transferred  to  Philadelphia,  Pa.,  where  it  is 
still  in  operation.  On  March  1,  1913,  the  Hoover  Steel  Ball  Co. 
of  Ann  Arbor,  Mich.,  was  organized  by  Mr.  Hoover  for  the 


10 


purpose  of  engaging  in  the  manufacture  of  high-grade  steel  balls 
to  take  the  place  of  those  imported  from  Germany.  When  the 
European  war  started  in  1914,  the  blockade  of  German  ports  by 
the  British  Navy  shut  off  the  supply  of  steel  balls  formerly 
exported  by  that  country  to  the  United  States,  and  the  insistent 
demand  of  consumers  for  balls  made  in  this  country  imposed 
a  heavy  strain  upon  the  facilities  of  domestic  producers.  Some- 
what similar  conditions  existed  in  all  branches  of  the  machinery 
trade,  making  it  difficult  for  the  ball  manufacturers  to  increase 
the  capacity  of  their  plants ;  but  the  management  of  the  Hoover 
Steel  Ball  Co.  showed  commendable  initiative  by  contracting 
for  the  entire  output  of  machine  building  firms  with  which  orders 
were  placed  for  special  machinery  required  in  ball  manufacture; 
and  these  firms  were  given  financial  assistance  to  enable  them 
to  handle  work  with  the  greatest  possible  rapidity.  As  a  result, 
the  Hoover  Steel  Ball  Co.  has  greatly  increased  its  capacity,  the 
growrth  being  well  illustrated  by  Fig.  1  and  the  illustration  in  the 
center  of  the  book,  that  show,  respectively,  the  original  factory  in 
which  the  firm  started  manufacturing  in  March,  1913,  and  the  plant 
as  it  appears  at  present.  An  idea  of  the  magnitude  of  the  business 
will  be  gathered  from  the  fact  that  the  consumption  of  steel 
runs  in  excess  of  500  tons  a  month,  and  calculated  on  the  basis 
of  J^-inch  balls,  the  daily  production  is  between  25,000,000 
and  30,000,000  balls  per  day. 


Fig.  1.     Original  Plant  in  which  Hoover  Steel  Ball  Co.  started  Manufacturing 
Operation  in  March,  1913. 


11 


RAW  MATERIAL  OF  THE  STEEL 
BALL  INDUSTRY 

THE  steel  from  which  balls  are  made  comes  to  the  factory 
in  coils  or  straight  rods,  according  to  its  size.  Stock 
less  than  11/16  inch  in  diameter  comes  in  coils  and  is 
known  as  "wire,"  while  all  stock  exceeding  5/g-inch  in  diameter 
comes  in  straight  bars.  The  size  of  the  stock  is  referred  to  in 
thousandths,  i.  e.,  stock  ^g-inch  in  diameter  is  known  as  0.375- 
inch  stock.  The  following  is  a  specification  of  steel  wire 
used  for  making  balls:  carbon,  0.95  to  1.05  per  cent;  silicon, 
0.20  to  0.35  per  cent ;  manganese,  0.30  to  0.45  per  cent ;  chromium, 
0.35  to  0.45  per  cent;  sulphur  and  phosphorus,  not  to  exceed 
0.025  per  cent.  The  following  analysis  is  typical  for  the  larger 
sizes  of  stock  which  comes  in  straight  bars:  carbon,  1.02  per 
cent;  manganese,  0.40;  silicon,  0.21;  chromium,  0.65;  sulphur, 
0.026;  and  phosphorus,  0.014  per  cent.  A  well  equipped 
laboratory  is  maintained  in  which  chemical  and  physical  tests 
are  conducted  on  each  shipment  of  steel  to  determine  its  suit- 
ability for  manufacture  into  balls,  and  an  unloading  ticket  must 
be  signed  by  the  head  of  the  laboratory  before  the  steel  is  taken 
from  the  cars  into  the  plant.  Some  very  interesting  conditions 
have  been  brought  to  light  by  the  laboratory  work,  and  a  later 
section  of  this  article  will  be  devoted  to  a  discussion  of  tests 
conducted  on  the  raw  material  and  product,  data  obtained  from 
these  tests,  and  a  description  of  methods  and  apparatus  used 
in  the  laboratory. 

PRODUCTION  OF  BALL  BLANKS 
BY  COLD-HEADING 

BALL  blanks  made  from  stock  ranging  from  1/16  up  to  and 
including    j^-inch    m    diameter    are    formed    on    special 
cold-headers  designed  for  the  production  of  ball  blanks 
by   the   E.   J.  .Manville   Machine   Co.,   Waterbury,    Conn.     A 
battery  of  these  machines  is  shown  in  operation  in  Fig.  2,  and 
in  this  connection  it  may  be  mentioned  that  the  Hoover  Steel 
Ball  Co.  is  equipped  with  machines  of  the  following  sizes:  00,  0, 
1,  2,  3,  and  5.     Production  of  ball  blanks  by  the  cold-heading 
process  has  several  advantages  in  its  favor.     In  the  first  place, 
there  is  practically  no  waste,  with  the  exception  of  about  0.040 


Fig.  2.     General  View  in    Cold-header  Department;  Blanks  for  All  Sizes  of  Balls 
up  to  Y^-inch  Diameter  are  made  on  Cold-Heading  Machines. 


inch  of  metal  left  on  the  blank  to  provide  for  finishing.  Blanks 
can  be  held  to  this  close  limit  because  the  steel  is  worked 
cold  and  there  is  no  tendency  for  it  to  become  decarbonized. 
One  man  can  look  after  three  or  four  machines,  so  that  the 
cost  of  labor  is  almost  negligible.  Cold-headers  used  in  the 
production  of  ball  blanks  are  of  the  type  commonly  known  as 
single-blow  solid-die  machines,  and  the  way  in  which  they 
operate  can  best  be  explained  in  connection  with  Fig.  3.  These 
machines  consist  of  a  heavy  framed  which  completely  surrounds 
the  working  parts  of  the  machine,  thus  insuring  a  high  degree 
of  rigidity.  At  one  end  of  the  machine  there  is  a  driving  shaft 
B ;  and.  at  the  opposite  end  of  the  frame  is  die-block  C.  Between 
the  sides  of  the  frame  is  a  movable  ram  D  that  actuates  the  heading 
punch  E.  Wire  F  to  be  made  into  ball  blanks  enters  the  machine 
through  feed  rolls  G  and  then  passes  through  cut-off  quill  H. 
At  the  side  of  the  machine  is  supported  a  bracket  /  in  which 
slide  /  may  be  reciprocated  by  a  crank  motion  from  the  main 
driving  shaft.  Slide  J  has  a  cam  groove  cut  in  it  in  which  roll  K 
is  fitted ;  this  roll  is  mounted  on  cross-slide  L,  so  that  a  lateral 


13 


Fig  3.  Plan  View  of  Cold-header  Mechanism  Illustrating  Method  of  Operation. 

motion  is  imparted  to  cut-off  knife  M  located  on  the  end  of 
cutter-bar  L. 

A  ratchet  feed  advances  the  wire  through  the  cut-off  quill 
until  it  comes  into  contact  with  a  stop,  which  is  not  shown 
in  the  illustration.  This  stop  checks  forward  motion  of  the  stock 
when  a  sufficient  length  has  passed  the  cut-off  knife  to  produce 
a  ball  blank  of  the  proper  size.  Cut-off  knife  M  is  advanced  in 
the  manner  just  described,  severing  the  wire,  but  retaining  it  on 
the  cut-off  blade  by  means  of  a  spring  finger.  Advance  of  the 
cut-off  knife  and  wire  slug  is  continued  until  the  slug  reaches  a 
position  directly  in  front  of  the  opening  in  die  TV.  Here  it  is 
held  stationary  long  enough  for  punch  E  to  begin  to  push  the 
slug  of  metal  into  the  die,  at  which  time  cut-off  knife  M  retreats 

Table  I.     Capacities  of  Cold-headers  in  Ball  Blanks  per  Hour 


Size  of 
Cold- 
header 

Capacity  for 
Ball  Blanks 
Diameter  in 
Inches. 
Max.  Size. 

Production 
of  Blanks 
per  Hour 

Size  of 
Cold-header 

Capacity  for 
Ball  Blanks 
Diameter  in 
Inches. 
Max.  Size. 

Production 
of  Blanks 
per  Hour 

00 

3/16 

7800 

2 

7/16 

6300 

0 

9/32 

7200 

3 

1/2 

6000 

1 

3/8 

6900 

5 

9/16 

4800 

Note — Due  to  time  loss  in  setting  up,  trouble  with  stock  and  breakdowns,  the  actual 
average  rate  of  production  is  from  80%  to  90%  of  above  values. 


Table  II.    Size  of  Stock  Used  for  Making  Balls  on  Cold-headers 


Diameter  of 
Ball  —  Inches 

Diameter  of 
Stock  —  Inches 

Diameter  of 
Ball  —  Inches 

Diameter  of 
Stock  —  Inches 

1/8 

.100 

5/16 

.235 

5/32 

.120 

3/8 

.275 

3/16 

.145 

7/16 

.320 

7/32 

.170 

1/2 

.365 

1/4 

.190 

9/16 

.395 

9/32 

.220 

5/8 

.440 

and  allows  punch  E  to  continue  its  work  by  pushing  the  blank 
to  the  bottom  of  the  die  cavity.  After  the  slug  F  has  been 
headed  it  is  ejected  by  the  knock-out  pin  O  which  is 
advanced  by  the  mechanism  operated  by  lever  P,  which 
also  receives  its  motion  from  a  crank  at  the  side  of  the  machine 
connected  to  the  main  driving  shaft.  In  this  way  the  ball 
blank  is  knocked  out  of  the  die  and  dropped  through  an  opening 
into  a  receptacle  placed  to  receive  it,  this  being  clearly  shown  in 
Fig.  2.  Table  II  gives  the  diameter  of  stock  used  in  making 
blanks  for  several  different  sizes  of  balls,  and  is  presented  to 
show  the  enlargement  that  takes  place  during  the  heading 
operation.  Various  grades  of  steel*  have  been  used  for  making 
dies  employed  on  the  cold-headers,  but  the  most  satisfactory 
results  have  been  obtained  with  the  following  grades  ^'Sander- 
son" or  "Viking  Special"  made  by  the  Crucible  Steel  Co.  of 
America;  "Intra"  made  by  the  Hermann  Boker  Co.;  "Gyro" 
made  by  Braeburn  Steel  Co.;  and  tool  steel  made  by  William 
Jessop  &  Sons. 


HOT-FORGING  BALL 
BLANKS 

IT  HAS  previously  been  stated  that  blanks  for  balls  exceeding 
^g-inch  in  diameter  are  hot-forged  from  straight  bars,    and 
in  handling  this  work  multiple  dies  are  employed    which 
produce  strings  of  balls  containing  up  to  ten  balls,  according 
to  the  size.    The  stock  is  heated  in  "Frankfort"  furnaces  made 
by  the  Strong,  Carlisle  &  Hammond  Co.  of  Cleveland,  Ohio; 


15 


Fig.  4.     View  of  Stock  Racks  in  Hot-forging  Department  where  Ball  Blanks 
exceeding  Y^-inch  diameter  are  made. 


these  are  oil  furnaces  which  are  operated  with  oil  at  a  pressure 
of  8  pounds  per  square  inch,  and  air  at  a  pressure  of  2  pounds 
per  square  inch.  Twelve  bars  are  arranged  in  the  furnace  as 
shown  in  Fig.  5.  The  hammer-man  takes  out  the  bar  at  the 
left-hand  side  of  the  furnace,  and  after  forging  a  string  of  balls 
at  the  end  of  this  bar  and  cutting  it  up  into  individual  ball 
blanks,  returns  the  bar  to  the  furnace  at  a  point  at  the  extreme 
right.  In  this  way,  the  bars  are  used  in  rotation,  which  prevents 
any  bar  from  becoming  overheated.  This  is  a  matter  of  con- 
siderable importance,  because  the  furnaces  are  maintained  at  a 
temperature  somewhat  in  excess  of  1800  degrees  F.  in  order  to 
provide  for  heating  the  stock  as  rapidly  as  may  be  necessary; 
but  should  it  happen  that  steel  was  left  in  the  furnace  for  an 
undue  length  of  time,  there  would  be  danger  of  burning  the  steel. 

The  multiple  forging  dies  are  shown  in  detail  in  Fig.  6, 
in  which  it  will  be  seen  that  each  die  opening  is  elliptical;  the 
purpose  of  this  is  to  provide  a  clearance  space  at  each  side  into 
which  excess  metal  will  flow.  It  must  be  borne  in  mind  however, 
that  while  this  illustration  only  shows  four  die  openings,  the 
number  of  openings  runs  up  to  ten,  according  to  the  size  of  ball 
blanks  that  are  being  forged.  In  the  cross-sectional  views, 
the  dimensions  of  the  die  are  indicated  by  letters,  and  in  Table 
III  are  given  diameter  A  of  cherrying  cutter,  distanced  between 


16 


Fig.  6.     Type  of  Die  used  for  Hot-forging  Ball  Blanks  for  Balls  exceeding 
%-inch  Diameter. 


Table  HI.     Dimensions  of  Hot- forging  Dies  for  Ball  Blanks 


Diameter 
of  Ball, 
Inch 

Diameter 
A  of  Die, 
Inch 

Distance 
B  between 
Centers, 
Inch 

Depth  C  of 
Die,  Inch 

Depth  D,  of 
Bridge,  Inch 

Diameter  E 
of  Stock, 
Inch 

3/4 

0.775 

0.910 

0.387 

0.065 

0.625 

7/8 

0.905 

1.060 

0.452 

0.065 

0.729 

1 

1.035 

1.210 

0.517 

0.075 

0.823 

centers,  and  depth  C  to  which  the  cherrying  cutter  is  sunk  in 
making  the  dies  for  three  sizes  of  balls,  and  these  data  are 
presented  to  indicate  how  dimensions  of  the  dies  vary  for  differ- 
ent sizes  of  balls.  The  depth  D  of  the  gate  between  adjacent 
diesis  a  matter  of  considerable  importance,  because, it  determines 
the  size  of  the  neck  between  adjacent  balls,  which  is  depended 
upon  to  hold  the  string  of  balls  together  until  they  are  sheared. 
Also  this  depth  must  be  regulated  so  that  there  is  no  tendency 
to  draw  the  stock  adjacent  to  the  neck  and  form  a  pipe  in  the 
ball  blank,  which  would  have  a  highly  detrimental  effect  on  its 
structure.  A  land  of  approximately  one-third  the  diameter  of 
the  ball  is  provided  for  clearance  at  the  bottom  of  the  die  and 
the  upper  die  member.  The  dies  are  made  from  a  special  die 
steel  made  by  the  Ludlum  Steel  Co.  of  Watervliet,  N.  Y.,  or  from 


17 


Fig.  5.      "Frankfort"   Oil-heated  Furnaces  made  by  Strong,   Carlisle    & 
Hammond   Co.,  in  which  Bars    are    Heated   for    Hot-forging    Operation. 


"Firth-Sterling  Special,"  made  by  the  Firth-Sterling  Steel  Co., 
McKeesport,  Pa.  This  is  not  an  alloy  steel,  but  a  regular  tool 
steel  adapted  for  making  hot-forging  dies.  In  order  to  produce 
round  balls  in  such  dies,  the  bar  is  turned  between  each  stroke 
of  the  hammer,  which  results  in  bringing  the  balls  to  a  close 
approximation  of  the  spherical  form.  Along  one  side  of  each 
die  is  a  pipe  with  a  number  of  holes  drilled  in  it  through  which 
water  flows  onto  the  dies  and  work. 

In  purchasing  stock  for  the  production  of  ball  blanks  for 
the  hot-forging  method,  it  is  matter  of  considerable  importance 
to  have  all  bars  of  the  same  length.  This  is  due  to  the  fact  that 
when  there  is  considerable  variation  in  length,  some  bars  will 


18 


be  used  up  before  others,  with  the  result  that  it  is  necessary  to 
finish  up  a  number  of  short  pieces  in  the  furnace  before  putting 
in  an  entire  new  charge.  At  the  end  of  each  bar  there  is  left 
what  is  known  as  a  "short  end,"  and  experience  has  shown 
that  these  short  ends  cannot  be  forged  into  ball  blanks  of  the 
regular  size,  as  they  fail  to  fill  out  the  dies  properly.  On  this 
account,  short  ends  are  collected  and  forged  into  ball  blanks  of 
the  next  smaller  size.  By  ordering  stock  in  bars  of  a  specified 
length,  ' 'short-ends"  are  eliminated. 

After  being  forged,  the  hot  string  of  balls  is  taken  to  punch 
presses  made  by  the  Ferracute  Machine  Co.,  Bridgeton,  N.  J., 
which  are  placed  beside  the  Bradley  helve  hammers  on  which 
the  forging  operation  is  performed,  the  arrangement  being 
clearly  shown  in  Fig.  7.  The  punch  presses  are  equipped  with 
multiple  shearing  dies,  which  consist  of  a  lower  die  member 
with  holes  of  the  same  size  as  the  balls  and  a  multiple  punch 
carried  in  the  ram,  one  punch  being  in  line  with  each  opening 
in  the  die.  The  string  of  balls  is  dropped  into  place  and  the 


Fig.  7. 


C.   C.  Bradley  Hammer  and  Ferracute  Power  Press  in  which  a  String  of 
Ball  Blanks  is  Forged  and  Cut  up  into  Individual  Balls. 


19 


press  tripped,  resulting  in  pushing  the  balls  through  the  holes 
in  the  die  and  leaving  the  scrap  metal  which  is  brushed  off 
before  the  next  operation  is  performed.  The  bar  is  then  returned 
to  the  right-hand  side  of  the  heating  furnace,  as  previously 
mentioned,  and  is  moved  to  the  left  each  time  a  heated  bar  is 
removed,  until  it  reaches  the  extreme  left  ready  for  another  string 
of  balls  to  be  forged  from  the  heated  metal  at  its  end.  Three 
sizes  of  helve  hammers  made  by  C.  C.  Bradley  &  Son,  Inc., 
Syracuse,  N.  Y.,  are  used  for  forging  ball  blanks,  which  have 
capacities  for  striking  blows  of  125,  150  and  300  pounds. 


ELEVATION  OF  DIE  AND  PUNCHES 


PUNCH.  HOLDER 


FLAN  OF  DIE 


Figure  8.  Type  of  Die  used  for  Shearing  String  Forgings  into  Individual  Ball  Blanks. 


Fig.  8.  shows  the  construction  of  shearing  punches  used 
for  cutting  up  the  string  forgings  into  individual  ball  blanks. 
At  A  is  shown  the  form  of  punch-holder  used,  which  will  be  seen 
to  consist  of  a  cast-iron  shoe  with  four  set-screws  for  holding 
the  punches.  These  are  secured  in  a  clamp  B  which  is  made 
by  drilling  holes  of  the  proper  size  for  the  punch  shanks  in  a 
block  of  the  desired  form  and  then  sawing  this  block  in  half; 
the  punches  are  then  put  in  place  and  the  entire  clamp  secured 
in  punch-holder  A  .  The  diameter  C  of  these  punches  is  usually 
made  about  J^-inch  less  than  the  diameter  of  the  balls  in  the 
string  forging  that  is  to  be  cut  up.  A  plan  view  of  the  die  is 
shown  at  D,  and  it  will  be  evident  that  the  spacing  £  between 
holes  in  this  die  is  the  same  as  the  center  distance  between  the 


die  cavities  in  the  forging  die.  Also  a  bridge  is  provided  in  the 
shearing  die  of  sufficient  depth  to  retain  the  neck  left  between 
adjacent  ball  blanks  on  the  string  forging  while  the  balls  are 
pushed  through  the  die.  After  the  shearing  operation  has  been 
completed,  the  scrap  metal  is  brushed  off  the  shearing  die  before 
the  next  set  of  ball  blanks  is  cut  up. 

In  has  been  mentioned  that  balls  ranging  in  size  from  ^-inch 
up  to  about  2j^-inches  in  diameter  are  made  by  forging  strings 
of  blanks  according  to  the  process  which  has  just  been  described. 
In  the  case  of  the  larger  sizes  of  balls — from  &/%  to  4  inches  in 
diameter — single  blanks  are  usually  forged  under  a  steam 
hammer,  making  one  blank  at  a  time  at  the  end  of  the  bar. 
Slugs  of  the  proper  size  are  first  cut  off  to  the  required  length 
and  both  ends  chamfered,  the  length  of  stock  being  determined 
by  the  weight  of  the  finished  balls  after  making  a  proper  allow- 
ance for  the  material  removed  in  finishing.  These  blanks  are 
placed  in  the  oil  furnace  and  heated  to  a  forging  temperature; 
and  each  time  a  blank  is  removed  to  be  forged  a  new  slug  of 
metal  is  put  into  the  furnace  in  its  place.  Dies  used  for  this 
kind  of  forging  are  of  an  entirely  different  form  from  those  used 
in  string  forging;  they  are  cupped  out  to  the  desired  diameter, 
but  are  only  turned  to  a  depth  of  one-quarter  the  diameter  of 
the  ball  to  be  forged  and  are  not  relieved.  When  the  blank  has 
been  heated,  the  hammer-man  places  it  in  the  die  and  the  hammer 
is  worked  very  slowly  until  the  blank  begins  to  take  a  spherical 
shape,  when  quicker  and  heavier  blows  are  struck.  Owing  to 
the  shallowness  of  the  die,  the  operator  has  ample  room  to  turn 
the  ball  in  all  directions,  and  he  can  therefore  produce  an  almost 
perfect  sphere.  Blanks  up  to  8  inches  in  diameter  are  forged 
without  varying  more  than  0.005  inch  from  a  true  spherical  form. 

ROUGH  DRY-GRINDING 

THE  method  of  making  ball  blanks  varies  according  to  their 
size,  small  blanks  being  made  on  cold-headers  and  large 
blanks  forged  from  hot  metal  according  to  the  methods 
which    have    just    been     described.     After     this     preliminary 
work,  all  sizes  of  balls  go  through  essentially  the  same  treatment 
certain  minor  modifications  being  made  according  to  the  quality 
of  the  balls;  and  the  method  of  treatment  may  also  vary  some- 


what  in  the  case  of  balls  of  extremely  large  size.    These  modifica- 
tions from  standard  practice  will  be  taken  up  in  detail. 

Blanks   made   by   either   the   cold-heading   or  hot-forging 
process  are   first  sent   to   the  dry-grinding  room,   where   they 


Fig.  9.     Side  View  of  Dry-grinder,  showing  wheel  dropped  away  from  work,  a 

Charge  of  Balls  ready  to  be  dropped  into  Grinding  Position,  and  Ball 

being    measured  for   Size   in    Test   Indicator. 


22 


are  subjected  to  a  rough-grinding  operation  § before  going  to 
the  heat-treating  department.  This  rough-grinding  results  in 
removing  a  considerable  part  of  the  surplus  metal  and  bringing 
each  ball  to  a  much  closer  approximation  of  a  truly  spherical 
form  than  it  is  possible  to  obtain  in  forgings  made  by  either  of 
the  methods  that  have  been  described.  In  the  case  of  hot-forged 


Fig.  10.      Front  View  of  Grinding  Machine,  showing  Grinding   Wheel  raised  to 

Operating  Position  and  Tray  of  Ground  Balls  just  removed  from  Machine; 

Balls  seen  in  Ring  are  not  in  Grinding  Position 


23 


ball  blanks,  this  rough-grinding  also  removes  the  decarbonized 
steel  from  the  surface  of  the  blanks  produced  in  forging. 

An  exception  to  the  general  method  of  procedure  is  made 
in  the  case  of  balls  from  1/16  to  3/16  inch  in  diameter.  Such 
balls  are  not  dry-ground  before  being  heat-treated,  but  they 
get  a  rough  and  a  finish  dry-grinding  after  being  hardened. 
Figs.  9  to  11,  inclusive,  show  the  type  of  machine  on  which 
the  dry-grinding  operation  is  performed,  and  the  best  idea 
of  its  construction  and  method  of  operation  will  be  obtained 
by  reference  to  the  two  views  shown  in  Fig.  11.  The  main 


Fig.  11. 


Front  and  Side  Views  of  Dry-grinding  Machine,  illustrating 
Principle  of  Operation. 


parts  of  this  machine  consist  of  a  carborundum  grinding  wheel 
A  and  an  iron  ring  B  which  are  driven  in  opposite  directions. 
Two  rings  C  and  D  are  supported  by  spiders  in  such  a  way 
that  there  is  a  space  between  the  beveled  edges  of  the  inner 
and  outer  rings  sufficient  to  allow  ball  blanks  that  are  to  be 
ground  to  project  through  this  space.  In  the  side  view  of  the 
machine  illustrated  in  Fig.  11,  these  rings  are  shown  with  the 
wheel  lowered,  but  when  the  machine  is  in  operation  the  balls 
held  between  rings  C  and  D  are  in  contact  with  grinding  wheel 
A  ;  and  ring  B  presses  down  and  holds  them  against  the  grinding 


wheel.  In  order  to  provide  for  grinding  the  balls  uniformly, 
the  spindles  on  which  grinding  wheel  A  and  driving  ring  B  are 
carried  are  placed  eccentric  to  each  other,  which  results  in  giving 
the  balls  an  oscillating  motion  in  addition  to  their  motion  of 
rotation ;  and  as  a  result  of  this  combined  movement  all  surfaces 
of  the  ball  blanks  are  exposed  to  the  action  of  the  grinding  wheel, 
which  results  in  bringing  them  to  a  close  approximation  of  the 
spherical  form.  The  way  in  which  the  upper  and  lower  spindles 
of  the  machine  are  driven  is  best  illustrated  in  Fig.  9,  which 
shows  how  open  and  crossed  belts  are  brought  to  the  machine 
pulleys  from  an  overhead  countershaft. 

Probably  the  best  way  to  describe  the  operation  of  one  of 
these  dry-grinders  is  to  start  at  the  point  where  a  charge  of 
ball  blanks  has  been  ground  down  to  the  required  size  and  is 
to  be  removed  from  the  machine.  To  provide  for  doing  this, 
the  head  which  supports  grinding  wheel  A  is  carried  on  a  slide 
on  the  base  of  the  machine.  Secured  to  the  bottom  of  this  slide 
is  a  rack  E  that  meshes  with  a  pinion  at  the  end  of  cross-shaft  F. 
Keyed  to  the  opposite  end  of  shaft  F  is  a  worm-wheel  G  that 
meshes  with  a  worm  actuated  by  hand-wheel  H  that  provides 
fine  adjustment.  Secured  to  the  bed  of  the  machine  is  a  disk  /, 
and  in  order  to  drop  grinding  wheel  A  out  of  contact  with  the 
work  held  between  rings  C  and  D,  the  spring  latch  carried  by 
lever  J  is  withdrawn  from  a  notch  in  disk  /  and  the  lever  is 
moved  to  the  left  until  the  latch  engages  a  stop  notch  in  disk  /, 
which  limits  the  downward  motion  of  the  grinding  wheel.  It 
will  be  seen  that  sufficient  clearance  is, now  provided  between 
grinding  wheel  A  and  rings  C  and  D  to  enable  tray  K  to  be 
swung  into  position  to  catch  the  balls  when  they  are  discharged 
from  the  holding  rings. 

It  will  be  seen  that  inner  ring  D  is  supported  by  a  spider 
secured  to  the  lower  end  of  rod  L,  and  in  order  to  discharge 
the  ground  balls,  ring  D  is  dropped  by  pushing  down  lever  M. 
This  drops  the  inner  ring  and  allows  the  ground  balls  to  fall  into 
tray  K.  When  lever  M  is  released,  ring  D  is  returned  to  its 
original  position  by  means  of  a  compression  spring  N.  During 
the  time  that  the  charge  of  balls  in  the  machine  is  being  ground, 
a  fresh  charge  of  blanks  is  placed  in  the  space  between  driving 
ring ,5  and  outer  ring  C;  a  few  of  these  balls  will  be  seen  in  position 
in  Fig.  9.  After  the  ground  balls  have  been  removed  and  inner 


ring  D  has  been  returned  to  the  position  shown  in  Fig.  11,  it  is 
necessary  to  place  the  charge  of  new  blanks  in  position  to  be 
ground.  This  is  done  by  dropping  both  rings  C  and  D  sufficiently 
so  that  the  balls  held  between  outer  ring  C  and  driving  ring  B 
may  drop  into  position,  after  which  the  two  rings  are  returned 
to  the  location  shown  in  Fig.  11.  This  result  is  accomplished 
by  means  of  lever  O  that  is  carried  at  the  end  of  a  cross-shaft 
which  has  a  pinion  at  its  right-hand  end  meshing  with  the  rack 
P  cut  in  the  sleeve  that  supports  the  spider  on  which  outer 
ring  C  is  carried. 

In  order  to  drop  a  charge  of  balls  into  place,  the  spring 
latch  carried  by  lever  0  is  released  and  this  lever  is  pulled  forward 
which  results  in  dropping  both  rings  C  and  D,  due  to  the  fact 
that  rod  Z/,  supporting  inner  ring  D,  is  pinned  to  the  upper  end 
of  sleeve  P,  to  which  the  outer  ring  is  connected  by  means  of  the 
spider.  When  the  balls  have  been  dropped  into  position  as 
indicated,  grinding  wheel  A  is  raised  into  contact  with  the  work 


Fig.  12.     Special  Grinding  Machines  for  Grinding  Rings  shown  at 
C  and  D  in  Fig.  11. 


by  raising  lever  /.  Rings  C  and  D  are  ground  to  a  smooth  surface 
and  fine  edge  in  order  that  the  balls  may  run  freely  and  reach 
through  the  space  to  come  into  contact  with  the  grinding  wheel 
A.  This  is  done  on  special  grinding  machines,  the  method  of 
grinding  the  inner  and  outer  rings  being  clearly  illustrated  in 
Fig.  12.  Lever  Q  at  the  front  of  the  grinding  machine  operates 
a  clutch  that  provides  for  starting  or  stopping  the  machine. 
It  will  be  seen  from  Figs.  9  and  10  that  the  grinders  are  provided 
with  an  exhaust  system  to  carry  away  the  dust  of  the  wheel. 

HEAT  TREATMENT 

DURING  the  process  of  making  the  steel  for  the  balls  and 
in   forging   and    rough-grinding   the   ball   blanks    made 
from  this  steel,  severe  internal  strains  are  likely  to  be 
set  up  in  the  metal  that  would  often  be  of  sufficient  magnitude 
to  cause  the  balls  to  be  broken  when  subjected  to  only  a  small 


Fig.  13.     Charging  End  of  American  Rotary  Gas  Furnaces  in  which  Balls 
up  to  One  Inch  Diameter  are  Heat-treated. 


part  of  their  rated  load  carrying  capacity.  Trouble  from  this 
source  must  be  eliminated,  and  this  is  done  by  subjecting  the 
balls  to  a  preliminary  annealing  operation  in  rotary  gas  furnaces 
made  by  the  American  Gas  Furnace  Co.  of  Elizabethport,  N.  J., 
before  the  final  hardening  operation.  The  same  type  of  furnace 


Fig.  14.     Discharge  End  of  American  Rotary  Gas  Furnaces,  showing  Quenching 

Tanks  and  Deflector  through   which  Balls  are  delivered  to 

Baskets  at  Bottom  of  Tanks. 


is  used  for  the  annealing  and  hardening  operations,  but  for  the 
former  the  delivery  chute  on  the  furnace  is  arranged  to  discharge 
the  balls  into  pans,  as  shown  at  A  in  Fig.  13,  while  for  the  latter 
the  balls  are  discharged  into  a  quenching  tank,  as  indicated  in 
Fig.  14.  The  form  of  retort  used  in  these  American  gas  furnaces 
is  shown  in  Fig.  15,  and  it  will  be  seen  to  have  a  spiral  path 


Fig.  15.  Cross-Sectional  View  of  "Nichrome"  Retort  used  in  Rotary  Gas  Furnaces. 

through  which  the  balls  pass  as  the  retort  is  revolved.  At  the 
loading  end  of  each  furnace  there  is  a  hopper  that  is  kept  filled 
with  ball  blanks,  and  the  retort  draws  blanks  from  this  hopper 
and  passes  them  through  the  furnace  at  such  a  rate  that  the 
steel  is  heated  to  the  desired  temperature  when  the  balls  are 
discharged.  For  annealing,  a  temperature  of  1300  degrees  F. 
is  employed,  and  for  hardening  the  balls  are  raised  to  a  tempera- 
ture of  from  1425  to  1475  degrees  F.  according  to  the  size  and 
the  composition  of  the  steel.  Pyrometers  made  by  the  Hoskins 
Mfg.  Co.  of  Detroit,  Mich.,  are  used  to  determine  the  tempera- 
ture of  each  furnace. 


QUENCHING  THE  STEEL 
BALLS 

IT  HAS  been  mentioned  that  the  same  type  of  furnace  is 
used  for  both  the  annealing  and  hardening  operations,  the 
only  change  being  to  place  the  tube  so  that  the  ball  blanks 
are  discharged  into  a  pan  in  the  case  of  annealing,  and  into 
the  quenching  tank  in  the  case  of  the  hardening  operation. 
The  retorts  used  in  the  furnaces  were  formerly  made  of  cast 
iron,  and  great  trouble  was  experienced  through  their  destruction 
after  they  had  been  in  service  a  short  time.     This  trouble  has 


been  over-come  by  substituting  "Nichrome"  in  place  of  cast  iron, 
and  retorts  made  of  this  material  last  indefinitely. 

In  hardening,  there  is  a  difference  of  practice  according  to 
the  size  of  the  balls,  those  of  5/16-inch  diameter  and  less  being 
quenched  in  oil  while  balls  of  larger  size  are  quenched  in  water. 
Balls  made  of  some  grades  of  steel  are  quenched  in  pure  water 
and  others  are  quenched  in  brine.  In  all  cases  the  quenching 
tanks  are  provided  with  a  device  of  the  form  shown  in  Fig.  14, 
which  consists  of  a  series  of  conical  sheet  metal  deflectors  through 
which  the  balls  pass  before  reaching  the  wire  mesh  basket  at 
the  bottom  of  the  tank.  The  purpose  of  these  sheet  metal  cones 
is  to  deflect  the  course  of  the  balls  so  that  they  follow  a  winding 
path  and  are  completely  cooled  before  reaching  the  bottom  of 
the  tank.  One  complete  furnace  charge  can  be  run  into  one 
of  these  wire  baskets  and  when  this  is  filled,  the  entire  outfit 
is  lifted  out  of  the  tank  by  means  of  an  electric  hoist  as  shown, 
and  the  balls  are  then  removed  from  the  basket.  The  depth  of 


Fig.  16.    ''Frankfort"  Oil  Furnaces  for   use  in  Heat-treating  Balls  over   One  inch 

Diameter,  and  Quenching  Tank  in  which  these  Balls  are  Hardened.  Note 

Hoskins  Pyrometer  for  showing  Temperature  of  Furnaces. 


30 


the  quenching  tank  is  about  14  feet.  Rotary  furnaces  are  used 
for  annealing  and  hardening  the  smaller  sizes  of  balls,  and  in 
the  case  of  balls  one  inch  in  diameter  and  over,  ''Frankfort" 
oil  furnaces  are  employed,  into  which  the  balls  are  introduced 
on  trays  as  shown  in  Fig.  16.  When  the  balls  are  heated  to  the 
proper  temperature,  these  trays  are  withdrawn  and  the  balls 
are  dumped  into  the  quenching  tanks  provided  with  the  sheet 
metal  cones  described.  The  reason  for  quenching  small  balls 
in  oil  and  large  balls  in  water  is  that  the  oil  does  not  absorb  the 
heat  as  rapidly  as  the  water,  and  in  the  case  of  very  small  balls, 
the  shock  of  dropping  them  into  water  would  result  in  strains 
so  great  that  many  balls  would  either  be  cracked  or  broken,  and 
the  strength  of  those  balls  in  which  there  were  no  visible  defects 
would  be  seriously  impaired.  In  the  case  of  large  balls,  there 
is  sufficient  heat  to  prevent  trouble  from  this  cause.  From 
time  to  time  sample  balls  are  tested  by  breaking  them  on  an 
anvil  and  examining  the  structure  of  the  steel  to  make  sure  that 
the  heat-treatment  is  producing  the  desired  results.  Provision 
must  be  made  for  preventing  over-heating  of  the  oil  or  water 
in  the  quenching  baths,  and  this  is  done  by  having  a  circulating 
system  through  which  the  oil  or  water  passes  into  a  reservoir 
outside  the  building  and  then  through  a  coil  in  this  reservoir 
and  back  to  the  tank.  In  this  way  the  contents  of  the  quenching 
tank  are  kept  in  continual  circulation,  preventing  overheating. 

SPECIAL  TREATMENT  TO  RELIEVE 
INTERNAL  STRAINS 

DURING  the  process  of  hardening,  internal  strains  are 
set  up  in  the  balls,  and  it  is  necessary,  of  course,   to 
relieve  the  strains  without  effecting  the  surface  hard- 
ness of  the  balls. 

This  is  done  by  immersing  the  balls  which  are  carried  in 
wire  baskets,  in  a  tank  of  boiling  water  for  two  hours.  The 
equipment  used  for  this  purpose  is  shown  in  Fig.  17. 

This  practice  is  only  followed  in  the  case  of  balls  that  are 
hardened  by  quenching  in  water  or  brine. 

Besides  relieving  the  internal  strains,  the  hot  water  prevents 
the  balls  from  rusting  after  their  removal,  as  the  hot  balls  dry 
off  very  rapidly. 


Fig.  17.  Water  Bath  in  which  Severe  Strains  are  Removed  from  Balls  Quenched 
in  Water  by  subjecting  them  to  Temperature  of  Boiling  Water  for  Two  Hours. 
This  Treatment  also  enables  Balls  to  Dry  Rapidly  and  Prevents  Rusting. 


FINISH 
DRY-GRINDING 

AFTER  being  hardened,  the  balls  are  sent  back  to  the  dry- 
grinding  room,  where  they  are  subjected  to  what  is 
known  as  a  finish  dry-grinding  operation.  This  is  the 
same  as  the  rough  dry-grinding  that  the  balls  receive  before  harden- 
ing, except  that  it  is  done  with  a  finer  wheel  which  results 
in  removing  the  scale  produced  in  hardening  and  also 
reducing  their  diameters  a  little  closer  to  the  finished  size. 
For  the  rough-grinding  operation,  wheels  of  No.  40  grit  are 
employed.  On  the  finish-grinding,  the  grit  of  the  wheel  varies 
according  to  the  size  of  the  balls.  Wheels  of  No.  60  grit  are 
used  for  all  balls  exceeding  5/16-inch  in  diameter,  while  for 
smaller  balls  wheels  of  90  or  100  grit  are  employed.  In  all  cases 
the  machines  are  driven  at  the  required  number  of  revolutions 
per  minute  to  give  a  surface  speed  of  4500  to  5000  feet  per  minute 
at  the  point  where  the  ring  wheel  engages  the  balls. 


A  VISITOR  who  is   conducted   through   the   plant  of    the 
Hoover  Steel   Ball   Co.   finds  it  exceptionally    easy    to 
become  acquainted  with  what  is  going  on  in  each  shop, 
because,    although     the     plant     is     large,     it    is    engaged    in 
making  a  single  product,  manufacturing  operations  on  different 
sizes  of  balls  being  conducted  in  essentially  the  same  way  through 
out.    This  condition  stands  out  in  marked  contrast  to  that  found- 
in  plants  engaged  in  the  production  of  a  variety  of  different 
parts,  as  the  manufacturing  operations  necessarily  vary,  making 
it  more  difficult  to  see  just  what  is  being  done. 


c  •  oce  *Dm  ©E©  c>Fo 


Fig.  18.      (A)   String  of  Hot- forged  Bail  Blanks.      (B}Ball  Blanks  made  by  Cold- 
heading  Process.    (C)  Rough  Dry-ground  Balls.    (D)  Rough  Dry-ground  Balls  after 
Hardening.      (E)  Finish  Dry-ground  Balls.       (F)  Oil-rolled  Balls.       (G)  Oil-ground 
Balls.     (H)  Polished  Balls  ready  for  Inspection. 


Fig.  18  shows  the  condition  of  the  product  at  each  step  in 
the  process  of  manufacture,  and  it  will  be  of  interest  to  study 
this  illustration  carefully,  as  it  shows  just  what  is  done  to  the 
balls  by  each  operation  through  which  they  pass  before  comple- 
tion. At  A  is  shown  a  string  of  hot-forged  ball  blanks  before 
they  have  been  sheared  apart,  and  at  B  are  illustrated  two  ball 
blanks  made  by  the  cold-heading  process.  Blanks  produced 
by  either  of  these  methods  are  first  subjected  to  a  rough  dry- 
grinding  operation  which  reduces  them  to  an  approximately 
spherical  form,  as  shown  at  C,  although  the  surface  is  covered 
with  a  multitude  of  small  flats  and  scratches  left  by  the  grinding 
wheel.  At  D  are  shown  two  rough-ground  blanks  after  they 
have  been  subjected  to  the  process  of  heat-treatment,  and  it 
will  be  noticed  that  their  appearance  is  essentially  the  same  as 
that  of  the  rough-ground  blanks  shown  at  C  except  that  the 
surface  is  darkened  as  a  result  of  the  heat  treatment.  Two 
blanks  are  shown  at  E,  which  have  received  the  finish  dry- 
grinding  after  being  hardened,  and  it  will  be  noticed  that  the 
appearance  of  these  blanks  is  the  same  as  that  of  the  rough- 


33 


ground  blanks  C  except  that  the  flats  and  scratches  are  not  so 
pronounced.  At  F  and  G  are  shown  two  blanks  that  have  gone 
through  a  process  known  as  '  'oil-rolling"  and  two  blanks  that 
have  been  through  the  oil-grinding  process.  The  appearance  of 
both  these  balls  is  practically  the' same  except  that  the  oilground 
balls  have  been  reduced  to  exactly  the  desired  size.  At  H  are 
shown  two  finished  balls  after  being  polished,  ready  to  be  sent 
on  to  the  inspection  department,  where  they  will  be  subjected 
to  a  series  of  rigid  tests. 

OIL-ROLLING  BALLS  IN 
TUMBLING  BARRELS 

AFTER  receiving  the  finish  dry-grinding,  the  balls  are  of 
approximately  spherical  form,  but  the  surface  is  covered 
with  flat  spots  and  scratches  left  by  the  grinding  wheel 
and  there  is  still  a  considerable  amount  of  excess  metal  on  the 
balls  to  be  removed.    The  first  step  is  to  subject  them  to  a  process 
known  as  oil-rolling  which  consists  of  tumbling  a  charge  of  balls 
in  an  iron  barrel  containing  oil   and   abrasive.     This  oil  and 
abrasive  is  refuse  from  machines  on  which  a  subsequent  opera- 
tion known  as  "oil-grinding"  is  performed;  this  operation  will  be 


Fig.  19.     View  in  Oil-rolling  Department,  showing  Special  Tumbling  Barrels 
of  Large  Capacity. 


34 


described  in  detail  later,  and  the  nature  of  the  abrasive  will  be 
explained  at  that  time.  Most  of  the  tumbling  barrels  used  in 
this  department  have  capacity  for  a  charge  of  1500  pounds  of 
balls,  and  these  were  built  especially  for  the  Hoover  Steel  Ball 
Co. ;  but  some  800-pound  barrels  made  by  the  Baird  Machine  Co. 
of  Bridgeport,  Conn.,  are  also  employed.  Some  of  these  barrels 
are  shown  in  operation  in  Fig.  19.  The  purpose  of  oil-rolling 
is  to  smooth  off  the  flats  and  scratches  left  by  the  dry-grinders 
and  to  remove  excess  stock,  about  0.004  inch  being  allowed 
for  removal  in  the  oil-grinding  operation.  Balls  up  to  1^2-inch 
in  diameter  are  given  this  oil-rolling  treatment. 

It  is  necessary  to  leave  the  balls  in  these  tumbling  barrels 
from  twenty  to  thirty-six  hours,  according  to  the  amount  of 
stock  that  must  be  removed,  and  as  each  ball  rotates  in  such  a 
way  that  its  entire  surface  is  uniformly  exposed  to  the  action 


Fig.  20.     Oil-grinding  Machine  on  which  Final  Grinding  Operation  is  performed 

— Attention  is  called  to  Dials  showing  Approximate  Time  when  Grinding 

will  be  Finished,  and  Indicator  for  Testing  Size  of  Balls. 


35 


of  the  abrasive  and  of  the  balls  adjacent  to  it,  this  treatment 
results  in  the  production  of  perfect  spheres.  When  the  time  has 
almost  arrived  at  which  the  balls  should  be  removed,  a 
number  are  selected  at  random  from  the  contents  of 
each  barrel,  taken  out  and  measured  with  a  micrometer 
in  order  to  see  how  closely  they  approach  the  required  size. 
The  oil-rolling  is  then  continued  with  successive  gaugings  until 
the  balls  have  been  reduced  to  the  required  dimension  plus  0,004 
inch,  after  which  they  are  removed  from  the  barrels,  cleaned, 
and  then  taken  to  the  oil-grinding  department.  In  reducing 
balls  by  the  process  of  oil-rolling,  it  occasionally  becomes  neces- 
sary to  add  more  abrasive  to  the  supply  of  oil  and  abrasive  ob- 
tained from  the  oil-grinders.  When  this  is  done,  No.  36  carborun- 
dum is  used,  as  this  coarse-grain  abrasive  increases  the  speed  at 
which  the  balls  are  reduced  to  the  required  size. 

HOW  THE  PROCESS  OF  OIL-GRINDING 
IS  CONDUCTED 

THERE  are  two  main  grades  of  balls  made  in  the  Hoover 
factory,  known  as   "Micro-chrome"  and    "Commercial" 
balls,  the  former  being  the  better  quality.   Both  grades  are 
reduced  to  the  final  size  by  the  process  known  as  "oil-grinding" 
that   is   conducted  on  machines  of  the  form  shown  in  Figs.  20 


Fig.  21. 


Side  and  Front  Views  of  Oil-Grinding  Machine, 
Illustrating  Method  of  Operation. 


36 


and  21.  The  construction  and  operation  of  the  oil-grinding 
machines  will  be  best  understood  from  Fig.  21,  which  shows 
details  of  its  construction.  These  machines  are  provided  with 
two  iron  rings  A  and  J3,  each  of  which  has  an  annular  groove  cut  in 
it  of  a  suitable  size  to  accommodate  the  balls  C  to  be  ground. 
It  will  be  noted  that  there  is  a  small  groove  at  the  bottom  of  the 
annular  groove  in  the  lower  ring  A ,  which  provides  for  holding  a 
supply  of  oil  and  abrasive.  Ring  A  has  the  annular  groove  for  the 
balls  cut  at  the  bottom  of  a  larger  groove,  and  ring  5  has  a  flange 
in  which  the  ball  groove  is  cut  that  drops  into  this  large  groove 
in  ring  A ;  the  arrangement  will  be  readily  understood  from  the 
illustration.  It  will,  of  course,  be  understood  that  the  grinding 
ring  is  rilled  with  balls,  the  number  that  constitutes  a  complete 
charge  varying  according  to  the  size  of  balls  that  are  being 
ground. 

To  provide  for  loading  and  unloading  the  machine,  lower 
ring  A  is  drawn  out  onto  a  table  D  which  is  provided  for  that 
purpose,  and  after  a  fresh  charge  of  balls  has  been  put  in  place 
this  ring  is  pushed  back  into  position  under  the  upper  ring  B 
that  is  secured  to  the  spindle  of  the  machine.  A  sheet  metal 
shield  is  then  pushed  into  place  in  front  of  the  rings  in  order  to 
prevent  splashing  of  the  oil.  Ring  A  is  located  in  approximately 
the  desired  position  by  means  of  a  hole  in  the  machine  bed 
into  which  an  extension  on  the  under  side  of  ring  A  drops,  but 
the  extension  on  this  ring  is  a  loose  fit  in  the  hole  to  allow  ring 
A  to  align  itself  properly  with  ring  B. 

The  upper  ring  is  secured  to  the  spindle,  and  in  order  to 
start  the  grinding  operation  it  must  be  lowered  into  contact 
with  the  balls  carried  in  the  annular  groove  of  ring  A.  This  is 
accomplished  by  a  rack  on  the  spindle  sleeve  that  meshes  with 
pinion  E  secured  to  lever  F. 

In  order  to  raise  ring  B  out  of  contact  with  the  work  so  that 
ring  A  may  be  drawn  out  onto  turntable  D,  lever  F  is  pulled  down 
into  the  horizontal  position  shown  in  the  illustration.  In  this 
position  spring  latch  G  drops  into  a  notch  on  ring  H  that  is 
secured  to  the  frame  of  the  machine,  thus  holding  ring  B  in  the 
suspended  position.  After  the  machine  has  been  reloaded  and 
it  is  desired  to  drop  ring  B  into  contact  with  the  work  preparatory 
to  starting  the  grinding  operation,  spring  latch  G  is  withdrawn 


from  the  notch  in  ring  H  by  pulling  back  grip  /  that  is  connected 
to  the  end  of  the  rod  on  which  latch  G  is  carried.  Then  the  wheel 
is  lowered  by  gravity,  care  being  taken  to  hold  tight  to  the 
crank  at  the  end  of  lever  F  so  that  it  is  slowly  raised  to  a  vertical 
position  instead  of  flying  up  and  allowing  ring  B  to  drop  heavily 
onto  the  balls  carried  in  the  lower  ring. 

It  will  be  seen  that  there  are  three  grinding  heads  provided 
on  each  machine,  and  these  are  furnished  with  independent 
tight  and  loose  pulley  drives,  so  that  any  head  may  be  stopped 
without  interfering  with  the  operation  of  the  other  two.  This 
is  done  by  throwing  the  belt  from  the  tight  to  the  loose  pulley 
by  means  of  lever  /,  which  actuates  the  belt  shifter.  The  oil- 
grinders  are  provided  with  a  dial  similar  to  that  of  a  clock, 
so  that  the  time  for  grinding  can  be  observed;  the  grinding 
operation  usually  takes  from  twenty  to  forty-five  minutes,  ac- 
cording to  the  size  of  the  balls  and  the  amount  of  stock  that 
must  be  removed.  When  the  machine  is  set  up  ready  to  start 
the  grinding  operation,  this  dial  is  set  to  the  approximate  time  at 
which  the  grinding  operation  will  be  completed,  and  a  little  while 
before  this  time  is  reached  several  balls  are  selected  at  random 
from  different  points  around  the  ring,  and  are  measured  with  an 
indicator  to  see  how  near  they  come  to  the  required  size.  The 
dials  on  the  machine  and  the  test  indicator  are  shown  in  Fig.  20. 


Fig.  22.    Small  Tumbling  Barrels  for  Cleaning  Balls  in  Sawdust,  and  Riddles  foi 
Separating  Sawdust  from  Balls. 


38 


CLEANING  AND  POLISHING 
OIL-GROUND  BALLS 

AS  SOON  as  the  balls  have  been  ground  down  to  the  desired 
diameter,  they  are  removed  from  the  machine  and  taken 
to   tumbling   barrels   containing   hardwood   sawdust,   in 
which  they  are  rolled  for  a  sufficient  length  of  time  to  clean  off 
all  oil  and  abrasive.    The  charge  in  each  tumbling  barrel  is  then 
taken  out  and  put  into  riddles  through  which  the  sawdust  is 
sifted,  as  shown  in  Fig.  22,  to  separate  it  from  the  balls;  the 
balls  next  go  to  the  tumbling  barrels  containing  a  mixture  of  oil 


Fig.  23.     Kegs  in  which  Balls  are  Polished  by  Rolling  in  Leather. 


39 


and  Vienna  lime.  They  are  rolled  in  this  mixture  for  a  sufficient 
length  of  time  to  give  them  a  preliminary  polish,  after  which 
they  are  removed  and  again  cleaned  in  tumbling  barrels  filled 
with  hardwood  sawdust.  The  sawdust  is  sifted  from  the  balls 
in  riddles,  after  which  they  are  rolled  for  from  twenty  to  twenty  five- 
minutes  in  kegs  containing  strips  of  kid  similar  to  that  from  which 
gloves  are  made,  the  arrangement  of  this  polishing  equipment 
being  shown  in  Fig.  23.  Rolling  the  balls  in  this  way  gives  them 
a  high  polish,  which  is  the  final  step  in  the  process ;  and  the  finished 
balls  are  then  ready  to  be  taken  to  the  inspection  department. 

The  following  data  concerning  conditions  under  which 
oil-grinders  are  operated  and  abrasives  and  oils  used  on  these 
machines  will  prove  of  interest.  It  has  been  mentioned  that 
two  main  grades  of  balls  are  made,  which  are  known  as  ' 'Micro- 
chrome"  and  ' 'Commercial"  the  former  being  the  better  quality. 
On  the  "Micro-chrome"  balls  the  grinders  are  run  at  195  revolutions 
per  minute  and  the  abrasive  used  is  a  mixture  of  No.  3-F  car- 
borundum and  "Atlantic  Red"  machine  oil  made  by  the  Standard 
Oil  Co.  On  "Commercial"  balls,  the  grinders  are  run  at  a  speed  of 
325  revolutions  per  minute  and  the  abrasive  is  an  equal  mixture 
of  Nos.  180  and  150  carborundum  to  which  No.  4  "Road  Oil" 
is  added,  this  oil  also  being  the  product  of  the  Standard  Oil  Co. 
Used  oil  and  abrasive  from  the  grinding  machines  is  collected 
and  used  in  the  tumbling  barrels. 

SPECIAL  TREATMENT  FOR 
LARGE  BALLS 

CERTAIN  variations  from  the  practice  described  in  the 
preceding  paragraphs  are  necessary  in  the  case  of  large 
sized  balls  which  would  be  too  heavy  to  handle  in  tumbling 
barrels.  For  instance,  "Commercial"  balls  over  1^-inch  in  diameter 
and  "Micro-chrome"  balls  over  5/g-inch  in  diameter  are  burnished 
on  oil-grinders  running  at  high  speed  and  in  which  very  fine 
abrasive  and  light  oil  are  used  instead  of  being  subjected  to  a 
tumbling  operation  in  barrels  containing  a  mixture  of  oil  and 
lime,  as  previously  described.  If  large  balls  of  this  kind  were 
put  in  a  tumbling  barrel,  there  would  be  too  much  shock  from 
the  balls  striking  one  another;  hence  the  variation  in  practice. 


40 


PRODUCTION  OF  OIL- 
ROLLED  BALLS 

IT  HAS  been  explained  that  in  the  regular  process  of  manu- 
facture the  balls  go  from  the  tumbling  barrels  to  the  oil- 
grinders  on  which  they  are  reduced  to  the  required  size 
ready  for  polishing.  There  are  some  cheaper  grades  of  balls, 
however,  that  do  not  go  to  the  oil-grinders;  these  balls  are  reduced 
to  size  by  oil-rolling  in  the  tumbling  barrels,  after  which  they 
are  polished  and  sent  to  the  inspection  department.  The  method 
of  polishing  is  the  same  as  that  to  which  the  better  grades  are 
subjected,  which  was  previously  described.  In  oil-rolling  the 
balls,  a  mixture  of  No.  36  carborundum  and  No.  4  "Road  Oil" 
is  used  in  the  tumbling  barrels. 

MANUFACTURE  OF  BRASS,  BRONZE 
AND  COPPER  BALLS 

IN  ADDITION  to  its  regular  product,  the  Hoover  Steel  Ball 
Co.  does  quite  an  extensive  business  in  the  manufacture  of 
brass,  bronze  and  copper  balls  of  various  sizes.  One  important 
use  of  these  balls  is  for  various  forms  of  valves,  although  they  find 
a  number  of  other  applications.  The  general  features  of  the 
methods  used  in  producing  these  balls  are  the  same  as  those 
employed  in  making  steel  balls,  but  there  are  certain  modifications 
which  will  prove  of  interest.  Brass,  bronze  and  copper  ball  blanks 
up  to  1  ^-inch  in  diameter  are  produced  on  Manville  cold-headers, 
and  blanks  for  balls  exceeding  this  size  are  cast.  In  the  case 
of  very  large  balls  the  practice  is  often  adopted  of  making  the 
blanks  hollow,  which  is  done  by  casting  them  with  a  sand  core 
that  is  subsequently  removed.  Then  in  order  to  prepare  the 
blank  for  finishing,  the  holes  left  by  the  core  prints  are  drilled, 
reamed  and  tapped  so  that  threaded  plugs  may  be  screwed  in. 
These  hollow  ball  blanks  are  then  subjected  to  the  regular  process 
of  manufacture,  and  it  is  a  difficult  matter  to  detect  the  place 
where  the  plugs  have  been  screwed  in. 

As  in  the  case  of  steel  balls,  these  blanks  are  first  subjected 
to  a  process  of  dry-grinding  to  make  them  approximately  spheri- 
cal. Brass,  bronze  and  copper  balls  are  too  soft  to  stand  treatment 
in  tumbling  barrels,  as  they  would  be  covered  with  bruises  from 
impact  with  each  other.  After  being  dry-ground,  they  receive 


41 


the  regular  process  of  oil-grinding  and  are  then  polished  in 
machines  of  the  same  design  as  those  used  for  oil-grinding;  but 
in  polishing,  the  balls  are  rolled  in  oil  without  any  abrasive, 
which  results  in  giving  them  quite  a  high  polish,  although  the 
surface  produced  is  not  as  highly  finished  as  in  the  case  of  steel 
balls  which  are  subjected  to  burnishing  and  polishing  operations 
after  being  oil-ground.  In  treating  brass,  bronze  and  copper  balls 
in  the  oil-grinding  machine,  care  must  be  taken  not  to  subject 
them  to  too  great  pressure,  and  in  order  to  guard  against  this 
the  rings  on  the  machine  are  filled  with  brass  and  steel  balls 
arranged  alternately;  the  steel  balls  support  the  pressure  of  the 
upper  ring  and  the  head  on  which  it  is  carried,  and  allow  the 
balls  to  be  ground  and  polished  without  being  subjected  to 
sufficient  pressure  to  flatten  them. 


INSPECTION  OF  FINISHED 
BALLS 

AFTER  each  step  in  the  process  of  manufacture,  the  balls 
receive  a  general  inspection  to  make  sure  that  nothing 
is  wrong  with  the  adjustment  of  the  machines  or  with  the 
material  from  which  the  balls  are  made  that  will  prevent  the 
production  of  balls  that  come  up  to  the  standard.    After  receiv- 
ing their  final  polish,   the  finished  balls  go  to  the  inspection 
department,  where  they  are  subjected  to  a  number  of  searching 
tests  in  order  that  all  defective  balls  may  be  eliminated  and 
that  those  balls  which   pass  inspection   may  be  divided   into 
various  grades  according  to  the  accuracy  of  their  dimensions. 

The  first  step  is  to  clean  the  balls  thoroughly,  which  is  done 
by  placing  them  in  metal  baskets  provided  with  long  handles 
so  that  the  load  of  balls  may  be  dipped  into  gasoline  to  remove 
grease  and  particles  of  leather  carried  over  from  the  polishing 
department.  After  this  washing,  the  balls  are  put  into  canvas 
bags  and  rolled  on  a  table  so  that  the  bags  will  absorb  the 
gasoline  and  wipe  off  the  dirt.  The  balls  are  given  a  preliminary 
wiping  in  one  of  these  bags,  after  which  they  are  placed  in  a 
second  bag  that  is  cleaner  and  insures  the  removal  of  the  last 
traces  of  gasoline  and  dirt. 


MAKING  PLATE 
INSPECTION 

AFTER  cleaning,  the  first  actual  examination  is  conducted 
on  what  are  known  as  "inspection  plates,  "one  of  which  is 
shown  in  Fig.  24.  These  plates  are  used  on  benches  that 
run  all  the  way  around  the  two  inspection  rooms,  so  that  ad- 
vantage may  be  taken  of  the  liberal  amount  of  daylight  provided 
by  the  windows  which  extend  from  below  the  bench  up  to  the 
ceiling.  The  plates  are  made  of  glass  and  painted  black.  A 
reflector  is  set  up  at  the  back  of  each  inspection  plate  which 
throws  light  on  the  balls;  and  a  strip  of  thin  flexible  cardboard  is 
drawn  back  and  forth  beneath  the  balls  to  rotate  them  and 
bring  all  surfaces  into  view.  Several  times  while  making  this 
inspection  all  the  balls  on  the  plate  are  rubbed  with  a  cloth 
to  change  their  axes  of  rotation  and  insure  exposing  the  whole 
surface.  The  first  step  is  to  pick  out  balls  having  cracks,  flats, 
etc.,  and  these  are  sold  as  seconds  or  scraps. 


Fig.  24.      Type  of  Glass  Plate  on  which  Preliminary  Inspection  is  Conducted. 


43 


During  the  next  step  in  the  process  of  inspection,  attention 
is  paid  to  a  white  spot  on  each  ball  that  is  thrown  from  the 
reflector  at  the  back  of  the  inspection  plate.  As  previously 
mentioned,  a  card  is  drawn  back  and  forth  under  the  plates 
to  make  them  revolve,  and  the  inspectors  first  pick  out  what 
are  known  as  "wigglers,"  which  is  the  name  given  to  balls 
that  are  out  of  round  and  go  through  a  series  of  contortions 
while  being  rolled.  After  this  has  been  done,  the  balls  on  the 
plate  are  gone  over  carefully  and  all  those  that  show  any  defect 
are  picked  out.  During  this  process  of  inspection,  the  balls 
are  sorted  into  eight  grades,  as  follows:  (1)  "Cracked,"  balls 
that  have  received  their  cracks  from  any  cause,  (2)  "Junk," 
balls  which  have  flats,  holes,  etc.;  (3)  "Rubbish,"  same 
defects  as  (2)  but  not  so  bad;  (4)  "Dead  soft,"  balls  that 
are  covered  with  small  pits  caused  by  impact  with  hard  balls 
during  the  process  of  tumbling;  (5)  "Out  of  round,"  balls  known 
as  "wigglers"  by  the  inspectors;  (6)  "Fifth  grade,"  balls  with 
small  cuts  and  scratches  on  them;  (7)  "Fourth  grade,"  balls 
showing  same  defects  as  "Fifth  grade,"  but  not  of  so  serious  a 
character;  (8)  Balls  having  no  defects  sufficiently  serious  to 
be  visible  to  the  eye.  The  inspectors  engaged  in  making  the 
plate  inspection  are  provided  with  small  magnets  somewhat  the 
shape  of  a  pencil  with  which  they  handle  the  balls  with  amazing 
dexterity. 

Disposal  of  the  defective  balls  varies  somewhat  according  to 
their  size.  Many  of  the  small  balls  with  defects  of  the  kind 
referred  to  are  sold  to  various  manufacturers,  according  to  the 
class  of  service  required  of  them.  For  instance,  very  poor  balls 
are  sold  to  novelty  makers.  Other  balls  that  are  not  good  enough 
for  use  in  high-grade  ball  bearings  are  plenty  good  enough  for 
the  use  of  certain  manufacturers  of  hardware  specialties,  such 
as  roller  bearing  castors  for  furniture,  roller  bearing  roller  skates, 
etc.  Large  balls  that  are  found  defective  are  returned  to  the 
manufacturing  department,  where  they  are  ground  down  to  a 
smaller  size  in  order  to  remove  the  defects  from  the  surface  of 
the  metal ;  and  these  balls  are  again  carried  through  the  regular 
process  of  manufacture. 


44 


GAUGING  BALLS  FOR 
SIZE 

BALLS  that  are  used  in  annular  bearings  must  be  of  abso- 
lutely the  same  size  in  order  to  give  satisfactory  results. 
If  this  is  not  the  case,  the  large  balls  will  support  all  the 
load,  and  the  undue  amount  of  service  to  which  they  will  be 
subjected  will  cause  them  to  be  destroyed  more  rapidly  than 
would  otherwise  be  the  case.  In  order  to  fit  properly  in"  the 
races,  it  is  desirable  for  the  balls  to  be  of  exactly  the  specified 
size,  but  provided  all  the  balls  are  of  the  same  size,  they  are 
capable  of  giving  very  satisfactory  results  even  though  they 
are  either  slightly  over  or  under  the  specified  size.  In  the 
final  process  of  inspection,  the  balls  are  gauged  and  sorted  out 
into  different  grades,  according  to  whether  they  are  of  exactly 
the  specified  size  or  somewhat  under  or  over  this  size.  Attention 
is  called  to  the  fact  that  this  variation  in  high-grade  steel  balls 
does  not  exceed-  a  few  ten- thousandths  inch.  As  balls  of  the 
different  grades  are  all  of  the  same  size,  they  are  capable  of 
giving  perfectly  satisfactory  results.  Some  users  of  balls  gauge 
them  at  their  own  plants  and  make  this  sub-division,  while  others 
buy  gauged  balls  ready  for  assembly. 

In  gauging  those  balls  which  show  no  defects  in  conducting 
the  plate  inspection,  practice  varies  according  to  the  size  of 
the  balls,  but  in  all  cases  the  object  is  the  same,  namely,  to 
sort  the  balls  out  into  those  which  are  of  absolutely  the  desired 
size  and  those  which  vary  by  different  degrees  either  above  or 
below  the  standard.  Balls  up  to  and  including  ^-inch  in  diameter 
are  gauged  on  automatic  machines  which  sort  them  into  seven 
different  grades,  as  follows:  balls  exceeding  0.0002  inch  over  size; 
balls  0.0002  inch  over  size;  balls  0.0001  inch  over  size;  balls  of  the 
specified  size;  balls  0.0001  inch  under  size;  balls,  0.0002  inch 
under  size;  and  balls  more  than  0.0002  inch  under  size.  Auto- 
matic gauging  machines  are  used  for  this  grading,  two  batteries 
of  such  machines  being  shown  in  Figs.  25  and  26.  The  balls 
are  placed  in  hoppers  A,  at  the  bottom  of  each  of  which  there 
is  a  plate  in  which  a  number  of  holes  are  drilled  in  a  ring,  these 
holes  being  of  slightly  larger  size  than  the  balls  to  be  gauged. 
The  plates  are  revolved,  and  as  each  hole  comes  into  line  with 
the  delivery  tube,  the  ball  carried  in  this  hole  drops  into  the 


45 


Fig.  25.     Close  View  of  Battery  of  Automatic  Gauging  Machines 
with  Inclined  Blades. 


tube  and  runs  down  over  gauge  blades  B  which  are  set  at  a  slight 
angle  to  each  other  so  that  balls  of  the  different  sizes  referred  to 
will  drop  between  the  gauge  blades  and  enter  tubes  that  carry 
them  to  the  proper  drawers  in  the  cabinets  beneath. 

It  will  be  seen  that  two  types  of  machines  are  shown  in 
Figs..  25  and  26.  In  Fig.  25  the  gauge  blades  are  placed  on  an 
incline  so  that  the  balls  run  over  them  by  gravity,  and  as  the 
balls  are  always  in  contact  with  the  gauge  blades,  the  tubes  lead- 
ing to  the  drawers  of  the  cabinet  can  be  placed  much  closer 
together  than  on  the  type  of  machine  shown  in  Fig.  26,  where 


46 


Fig.  26.     Close  View  of  Battery  of  Automatic  Gauging  Machines 
with  Horizontal  Blades. 


the  gauging  blades  are  in  a  horizontal  position.  On  the  latter 
type  of  machine  an  agitator  is  necessary  to  keep  the  balls  moving 
over  the  gauge  blades.  This  agitator  consists  of  a  crank  C  and 
connecting-rod  D  that  actuates  a  link  mechanism  which  causes 
a  horizontal  bar  to  rise  in  the  space  between  the  gauging  blades. 
This  bar  rises  slightly  and  then  moves  forward,  carrying  the 
balls  with  it,  after  which  the  agitator  bar  slowly  drops  and 
leaves  the  balls  once  more  supported  on  the  gauging  blades.  In 


47 


this  way  the  balls  are  moved  along  over  successive  tubes  and 
finally  drop  through  between  the  gauging  blades — the  position 
being  determined  by  the  size  of  the  balls — so  that  different  sizes 
of  balls  are  sorted  out  as  previously  described.  A  stop  checks 
the  progress  of  the  ball  as  it  passes  onto  the  gauging  blades,  and 
prevents  it  from  rolling  too  fast.  The  gauging  blades  are  set  by 
master  balls,  in  order  to  have  the  desired  angle  between  them; 
and  before  the  balls  are  packed,  the  accuracy  of  the  blade  setting 
is  tested. 

SPECIAL  INDICATOR  FOR 
TESTING  BALLS 

FOR  gauging  balls  larger  than  5/s-inch  in  diameter  use  is 
made  of.  an  instrument  of  the  form  shown  in  Fig.  27. 
This  will  be  seen  to  consist  of  an  ordinary  Brown  & 
Sharpe  dial  test  indicator  accurate  to  0.0001  inch,  that  is  set 


Fig.  27. 


Dial  Indicator  with  10  to  1  Leverage  Ratio,  for   Testing 
Accuracy  of  Balls  to  0.0001  Inch. 


48 


up  on  the  table  on  which  is  also  carried  a  holder  for  the  ball  to 
be  tested.  Connection  between  the  ball  and  the  dial  test  indicator 
is  made  by  a  lever,  the  fulcrum  of  which  is  so  placed  as  to  give 
a  ratio  of  1  to  10,  and  in  this  way  readings  obtained  are  accurate 
to  0.0001  inch.  The  girls  who  conduct  this  inspection  handle 
the  balls  very  rapidly  and  sort  them  out  into  different  sizes 
according  to  the  amount  of  deviation  from  the  normal  size. 

COUNTING  AND  PACKING 
BALLS 

IT  IS  necessary  to  use  great  care  in  handling  finished  balls  to 
prevent  them  from  becoming  rusty.     On  this  account  it 
would  not  do   to   have   the   balls   touched   by  the   fingers. 
For  these  reasons,  several  methods  of  mechanical  counting  have 
been  developed  which  give  extremely  satisfactory  results.    The 
apparatus    used    for    this    mechanical    counting    is    shown    in 
Fig.  28.       The  balls  are    placed    in    hopper    A    and    dropped 
down  in  holes   in    sliding    plate  B,    which    is    pushed    forward 
so  that  the  holes  are  under  the  hopper  during  the  "loading" 


Fig.  28.     Methods  used  for  Counting  Balls  Preparatory  to  Packing. 


49 


period.  The  plate  is  then  drawn  forward  to  allow  the  balls  to 
drop  out  into  a  box  placed  to  receive  them.  Each  stroke  of  the 
plate  counts  out  one  hundred  balls,  and  plates  for  counting  balls 
of  various  sizes  are  made  interchangeable  so  that  all  of  them 
may  be  used  on  a  given  machine.  Balls  up  to  J^-inch  in  diameter 
are  counted  by  the  machine,  and  balls  from  9/16  to  J/g-inch  in 
diameter  are  counted  mechanically  by  means  of  board  C,  into 
the  grooves  of  which  the  balls  are  loaded  up  to  an  index  line. 
Plates  of  this  kind  are  made  for  various  sizes  of  balls,  and  each 
plate  holds  500  balls.  Large  balls  are  counted  by  hand,  care 
being  taken  not  to  touch  the  balls  with  the  bare  fingers.  After 
counting,  the  balls  are  packed  in  cartons  lined  with  waxed  paper, 
and  these  are  packed  in  substantial  wooden  boxes  for  shipment. 

RESEARCH 
DEPARTMENT 

IT  IS  obvious  that  in  the  tonnage  manufacture  of  a  product 
that  must  meet  such  exact  requirements  as  balls  for  use 
in  high-grade  annular  bearings,  the  greatest  care  must  be 
taken  in  the  selection  of  raw  material  and  in  conducting  each 
step  in  the  process  of  manufacture  in  order  to  produce  balls 
that  will  pass  the  inspection  department.  In  addition  to  the 
requirements  of  high-grade  balls  that  were  referred  to  in  the 
description  of  various  examinations  that  are  conducted  by  the 
inspectors,  it  is  absolutely  necessary  for  the  balls  to  be  of  uniform 
hardness  and  strength  because  this  is  the  only  way  of  being 
sure  that  all  balls  will  possess  the  necessary  durability  and 
elasticity. 

Assurance  must  be  obtained  that  the  steel  received  at  the 
factory  is  of  a  suitable  grade  to  produce  balls  that  will  fulfill 
the  specifications  before  manufacturing  operations  are  started, 
because  if  the  balls  were  finished  before  it  was  found  that  they 
were  defective,  the  raw  material  and  the  labor  involved  in 
converting  this  material  into  finished  balls  would  be  lost.  Data 
showing  that  the  steel  fulfills  these  specifications  'are  obtained 
from  the  results  of  tests  conducted  in  the  testing  department 
which  is  equipped  with  all  the  necessary  apparatus  for  making 
physical  and  chemical  tests  upon  the  raw  material.  In  addition, 
this  department  is  referred  to  by  heads  of  the  various  manufac- 


50 


turing  departments  when  any  case  of  trouble  arises,  such  as  failure 
of  the  balls  to  harden  properly,  the  production  of  more  than  the 
usual  number  of  balls  with  cracks,  and  other  troubles  of  this 
kind.  Some  exceptionally  interesting  facts  have  been  brought  to 
light  as  the  result  of  work  conducted  in  the  metallurgical 
department  and  chemical  laboratory. 

TESTING 

RAW  MATERIAL 

THERE  are  sidings  from  the  Ann  Arbor  Railroad  entering 
the  plant  so  that  cars  may  be  run  directly  to  the  building 
in  which  the  raw  material  is  received  and  to  the  building 
where  the  finished  balls  are  packed  for  shipment.  The  method 
of  procedure  in  testing  raw  material  is  the  same  for  both  bar 
stock  and  coil,  and  consists  of  taking  at  random  a  number 
of  each  kind  in  proportion  to  the  quantity  received  and  from 
the  end  of  each  of  which  is  cut  a  sample.  One  end  of  this 
sample  is  etched  in  dilute  hydrochloric  acid  for  fifteen  minutes. 
After  this  has  been  done,  the  surface  of  the  metal  is  carefully 
examined  to  see  that  it  is  free  from  seams.  The  acid  tends  to 
accentuate  any  surface  defects  that  may  be  present,  so  that 
those  that  might  be  invisible  in  the  bar  as  it  comes  to  the 
plant  can  be  quite  easily  seen  after  the  treatment.  In  ball 
manufacture  it  is  highly  important  for  the  stock  to  have  a 
flawless  surface,  because  any  slight  defects  are  carried  right 
through  the  process  of  manufacture  and  are  likely  to  become 
accentuated,  with  the  result  that  balls  produced  from  this  stock 
will  be  rejected  by  the  inspectors. 

The  regular  routine  tests  of  the  raw  material  inspected  in 
the  laboratory  also  include  a  Brinell  hardness  test.  This  is 
especially  important  in  the  case  of  "wire"  under  11/16  inch  in 
diameter  that  is  converted  into  ball  blanks  by  the  cold-heading 
process,  because  excessive  hardness  of  this  material  is  likely 
to  give  trouble  through  the  breakage  of  the  cut-off  knives  or 
the  dies  used  on  the  cold-headers.  In  order  to  give  the  best 
possible  results,  stock  for  the  cold-heading  machine  should  have 
a  Brinell  hardness  of  not  over  170.  A  sufficient  number  of 
samples  to  represent  the  average  uniformity  of  the  shipment 
are  examined  for  pipes,  segration  or  decarbonization,  and  when 


51 


necessary  microphotographs  are  made,  which  together  with 
their  accompaning  reports,  put  definitely  on  record  the  condi- 
tion of  each  shipment.  Samples  are  also  taken  for  chemical 
analysis  from  each  shipment  and  the  percentage  of  the  most 
important  elements  determined,  this  being  influenced  by  the 
kind  of  material  received  and  the  effect  of  these  elements  on  the 
finished  product.  In  cases  where  laboratory  tests  do  not  show 
that  the  stock  is  defective,  an  "unloading  ticket"  is  made  out 
and  sent  to  the  stock- room,  authorizing  the  material  to  be 
taken  from  the  cars  and  placed  in  storage,  ready  to  be  drawn 
out  on  requisition  by  the  manufacturing  department. 

On  the  following  pages  are  given  our  specifications  for 
coil  and  bar  stock,  and  a  consideration  of  these  will  show  the 
care  taken  in  the  selection  of  raw  material  used  in  the  manu- 
facture of  Hoover  steel  balls. 


HOOVER    STEEL     BALL     CO. 

SPECIFICATION  NO.  1. 
Chrome-Carbon  Steel  Wire — Cold  Drawn. 


ANNULMENTS: 

1.  This  specification  supercedes  all  previous  specifications,  or  letters  of  instruction, 
covering  this  material. 

MANUFACTURE: 

2.  The  material  must  be  made  by  the  Electric  or  Crucible  process. 

QUALITY: 

3.  The  material  must  be  of  highest  quality  in  every  respect,  of  uniform  composition, 
and  free  from  slag  or  other  segregation. 

The  wire  must  be  free  from  imperfections,  such  as  pipes,  seams,  checks  or  lamina- 
tions either  on  the  surface  or  in  the  section  of  the  wire. 

WORKMANSHIP  AND  FINISH: 

4.  The  wire  must  be  of  good  workmanship,  must  have  a  good  surface  finish,  and 
must  be  true  to  diameter  ordered  within  the  limits  of  plus  .002"  and  minus  .002". 
If  the  wire  is  out-of-round,  the  mean  of  the  largest  and  smallest  measured  diameter 
must  be  equal  to  the  size  ordered,  but  in  no  case  can  they  exceed  the  limits  of 
plus  .002"  and  minus  .002". 

COMPOSITION: 

5.  Upon  receipt  of  the  material  at  destination,  drilling  may  be  taken  from  the 
several  coils,  selected  at  random,  for  analysis,  and  must  show  the  composition 
of  the  material  to  be  uniform  and  within  the  following  requirements. 

Carbon  .95  %     to  1.05  % 

Chromium  .35%     to     .45% 

Manganese  .80%     to     .45% 

Silicon  .20%     to     .35% 

Phosphorus  under  .025  % 

Sulphur  under  .025% 

CONDITIONS: 

6.  The  material  must  be  thoroughly  and  uniformly  annealed  and  the  fracture 
must  be  close  grained. 

The  Brinnell  hardness  (5  m/m  Ball  under  1000  Kg.  pressure)  must  not  exceed 
170  at  any  point  in  the  length  or  any  point  in  the  cross  section  of  the  wire,  so 
that  when  blanks  made  therefrom  are  cold  upset  into  the  form  of  a  Ball,  no 
defects  will  open  up  in  the  outside  surface  of  the  Ball. 

The  wire  must  be  free  from  any  decarbonized  surface  and  after  hardening  must 
show  a  close  grained  velvety  fracture. 

COIL  SIZE,  WEIGHT  AND  CONDITION: 

7.  Coils  must  be  reeled  uniformly  and  the  layers  must  be  bound  together  securely 
with  separate  tie  wires  to  keep  them  in  good  shape  during  transportation  so  that 
they  can  be  unwound  properly  without  tangling.     If  the  ends  of  the  coil  are 
tapered  down  or  imperfect  in  any  way,  they  must  be  "cropped"  off. 

Coils  may  be  covered  with  a  coating  of  oil  or  grease  to  protect  them  from  excessive 

rusting  during  transportation,  but  the  coils  must  be  free  from  any  hard  or  gritty 

foreign  matter  that  would  interfere  with  their  proper  operation  in  the   heading 

machine. 

The  coils  must  not  be  less  than  18"  inside  diameter  or  greater  than  34"  outside 

diameter.     Wire  of  heavy  cross  section  should  be  wound  in  as  large  a  coil  as 

possible,  but  within  the  outside  diameter  limit  given  above. 

The  coils  should  weigh  not  less  than  90  pounds  or  more  than  110  pounds  for  wire 

above  .235"  diameter.    Coils  of  wire  below  .235"  diameter  may  weigh  as  low  as 

70  pounds. 

REMARKS: 

8.  Material  which  fails  to  meet  the  above  requirements  will  be  rejected  and  returned. 
The  manufacturers  must  pay  all  transportation  charges  on  rejected  material. 
Ann  Arbor,  Mich.,  January  1st,  1917. 


53 


HOOVER     STEEL     BALL     CO. 

SPECIFICATION  NO.  5. 
Chrome-Carbon  Steel  Bars— Hot  Rolled. 

ANNULMENTS: 

1      This  specification  supercedes  all  previous  specifications  or  letters  of  instruction 
covering  this  material. 

MANUFACTURE: 

2.  The  material  must  be  made  by  the  Electric  or  Crucible  process. 

QUALITY: 

3.  The  material  must  be  of  highest  quality  in  every  respect,  of  uniform  composition, 
and  free  from  slag  or  other  segregation. 

The  bars  must  be  free  from  imperfections  such  as  pipes,  seams,  checks  or  lamina- 
tions either  on  the  surface  or  in  the  section  of  the  bar. 

WORKMANSHIP  AND  FINISH: 

4.  The  bars  must  have  as  good  a  surface  finish  as  is  consistent  with  good  hot  rolling 
practice.    They  must  be  free  from  excessive  scale,  and  must  be  true  to  diameter 
ordered  within  the  following  limits. 

Minus  0  and  plus  .005"  for  sizes  under  13/16"  diameter. 

Minus  0  and  plus  .010"  for  sizes  over  13/16"  diameter. 

If  the  bar  is  slightly  out-of-round,  the  mean  of  the  largest  and  smallest  measured 
diameter  must  be  within  the  minus  and  plus  limits  given  above. 
Appended  to  this  specification  is  a  table  giving  the  prevailing  sizes  (diameter) 
of  stock  which  we  use,  and  the  corresponding  decimal  sizes.  We  reserve  the 
right  to  change  this  list  from  time  to  time  when  necessary  but  the  order  or  contract 
calling  for  the  material  will  specify  the  size  wanted. 

As  an  example,  if  our  order  calls  for  13/16"  plus  .010"  (Decimal  .823"),  the 
manufacturer  may  supply  this  as  large  as  .833"  diameter  but  no  smaller  than 
.823"  Diameter. 

COMPOSITION: 

5.  Upon  the  receipt  of  material  at  destination,  drillings  may  be  taken  from  the 
several  bars,  selected  at  random  for  analysis,  and  must  show  the  composition 
of  the  material  to  be  uniform  and  within  the  following  requirements. 

Carbon  .90%     to  1.00% 

Chromium  .60%     to     .70% 

Manganese  .30  %     to     .45  % 

Silicon  .20%     to     .35% 

Phosphorus  under     .025  % 

Sulphur  under  .025  % 
CONDITIONS: 

6.  The  material  must  be  thoroughly  hotvworked  to  produce  a  fine  grain  and  must 
not,  subsequent  to  this  hot  working,  be  subjected  to  a  high  temperature  such 
as  would  produce  a  coarse  grain. 

The  surface  of  the  bars  must  be  free  from  decarbonization  to  the  extent  that  upon 
removing  .005"  from  the  diameter  of  the  bar,  the  remaining  section  will  retain 
its  full  quota  of  carbon  as  called  for  under  composition. 

The  bars  must  be  cut  to  uniform  lengths  as  ordered.  A  preferred  length  will  be 
specified  on  the  order,  also  a  minimum  length  and  a  maximum  length,  but  in  no 
case  may  intermediate  lengths  be  supplied.  For  example,  a  13/16"  plus  .010" 
diameter  bar  will  be  ordered  cut  to  lengths  64",  73"  and  82"  with  73"  as  the 
preferred  length. 

SHIPPING: 

7.  When  two  or  more  different  sizes  are  shipped  together  in  the  same  car,  they  must 
be  so  arranged  and  located  in  the  car  that  they  will  not  become  mixed  during 
transportation . 

REMARKS: 

8.  Material  which  fails  to  meet  the  above  requirements  will  be  rejected  and  returned. 
The  manufacturers  must  pay  all  transportation  charges  on  rejected  material. 
Ann  Arbor,  Mich.,  January  1st,  1917. 


54 


TESTS  OF  SEAMY  COLD- 
DRAWN  WIRE 

IN  DESCRIBING  the  inspecting  of  balls,  reference  was  made 
to  the  rejection  of  those  in  which  cracks  are  found. 
These  exist  almost  entirely  in  balls  up  to  and  including 
5/8-inch  in  diameter,  the  blanks  for  which  are  made  by  the  cold- 
heading  process;  it  seldom  happens  that  cracked  balls  are 
found  in  sizes  over  j^-inch,  blanks  for  which  are  made  by  the 
process  of  hot-forging.  A  study  of  this  subject  reveals  the 
fact  that  after  cold-heading,  ball  blanks  very  often  had  some 
sort  of  crack,  and  in  a  great  many  cases  these  were  quite 
deep.  At  first  it  was  thought  that  this  was  due  to  faulty 
annealing  or  to  some  element  in  the  steel,  which  had  a  tendency 
to  make  the  metal  brittle,  but  subsequent  investigation  showed 
that  this  was  not  the  case. 


STUDY  OF  SEAMS  IN  STEEL 
BARS  AND  WIRE 

DEFECTS  revealed  by  etching  the  metal  in  dilute  hydro- 
chloric acid  run  lengthwise  of  the  bar;  sometimes  these 
extend  for  the  entire  length  of  the  coil,  while  in  other  cases 
only  one  end  is  found  to  be  defective.  For  want  of  a  better 
name,  the  laboratory  has  called  these  defects  ' 'seams,"  and  it 
has  been  proved  that  wire  with  seams  will  in  all  cases  be  split 
to  some  extent  during  the  process  of  cold-heading,  while  that 
without  seams  will  produce  perfect  balls  in  the  cold-heading 
machines.  In  some  cases  the  cracks  opened  up  in  the  balls  while 
cold-heading  are  not  so  deep  that  they  cannot  be  eliminated  dur- 
ing the  subsequent  treatment  to  which  the  blanks  are  subjected ; 
but  in  other  cases  it  may  happen  that  these  splits  in  the  blanks 
are  so  deep  that  they  reach  below  the  surface  of  the  finished 
balls,  in  which  case  the  balls  will  be  rejected  by  the  inspectors. 
The  investigation  conducted  in  the  laboratory  relative  to 
troubles  resulting  from  stock  having  seams  or  scratches  have 
developed  the  following  information:  (1)  Cold-drawn  wire 
on  which  the  surface  is  apparently  quite  smooth,  and  on  which 
no  seams  are  visible,  is  found  in  many  cases  to  possess  minute 
laps  or  seams  which  are  made  visible  by  etching  with  dilute 


55 


hydrochloric  acid.  (2)  Although  these  seams  may  not  be  deep 
on  the  original  wire,  they  are  accentuated  by  the  stretch  which 
the  surface  of  the  wire  undergoes  during  the  cold-heading 
operation.  (3)  Such  cracks  are  likely  to  be  still  further  ac- 
centuated in  hardening,  and  in  many  cases  they  will  cause  the 
ball  to  split  in  half. 

In  making  a  study  of  the  effect  of  seams  on  the  steel, 
it  is  the  practice,  as  previously  mentioned,  to  etch  the  stock 
with  dilute  hydrochloric  acid  for  fifteen  minutes. 

The  action  of  the  acid  first  lays  open  any  surface  defects 
which  may  be  closed  so  tightly  by  the  pressure  of  the  cold- 
drawing  operation  that  they  will  be  invisible  to  the  eye 
unless  subjected  to  the  acid  treatment.  The  acid  also  makes 
the  cracks  black,  and  subsequent  grinding  exposes  the  white 
surface  of  the  adjacent  metal  so  that  the  crack  is  brought  into 
as  great  prominence  as  possible. 

TESTING  FOR  SEAMS  IN  STOCK  BY 
APPLICATION  OF  PRESSURE 

RECENTLY  another  test  for  revealing  these  seams  has 
been  developed,  which  consists  of  upsetting  short  blanks 
cut  from  the  bars.    These  test  blanks  for  wire  having  a 
diameter    of    .275",    are    7/16-inch    high    and    are    ordinarily 


B 


Fig.  33.     (A)  Samples  cut  from  Steel  with  Seam  in  Surface,  and  Same  Samples 

partially  and  fully  upset,  indicating  how  Seam  opens  up  through  Application 

of  Pressure;     (B)  Similar  Samples  from  Steel  without  Seam,  which 

show  No  Tendency  to  Split. 


56 


subjected  to  a  pressure  of  20,000  pounds,  which  results  in 
flattening  them  out  to  a  height  of  3/16-inch,  or  to  a 
pressure  of  50,000  pounds,  which  flattens  them  out  to  a 
height  of  3/32-inch.  In  all  cases  where  there  are  seams  in  the 
wire,  these  test  samples  are  split  open  by  this  pressure,  while  a 
perfect  wire  without  any  seams  is  not  damaged  by  the  treat- 
ment. At  A  in  Fig.  33  is  shown  a  sample  cut  from  wire  con- 
taining a  seam  and  the  same  blank  partially  and  fully  upset; 
it  will  be  noticed  that,  although  the  seam  in  the  wire  is  small, 
it  has  been  widened  out  considerably  by  the  upsetting.  At  B 
in  the  same  illustration  is  shown  a  similar  set  from  perfect  wire, 
comprising  a  blank  and  partially  and  fully  upset  samples,  and 
it  will  be  seen  that  the  upset  sample  does  not  show  any  tendency 
to  split. 

In  order  to  give  some  idea  of  the  extent  to  which  the  seam 
at  A  was  deepened  by  the  upsetting  treatment,  section  a-b 
through  the  blank  and  section  c-d  through  the  flat  disk  were 
polished,  and  photomicrographs  of  these  are  shown  in  Fig.  34. 
At  A  in  Fig.  34  the  seam  in  the  original  wire  was  about  0.010 
inch  in  depth,  while  at  B  the  depth  of  the  seam  after  the  blank 
has  been  upset  has  been  increased  to  approximately  0.050  inch. 
From  this  it  will  be  apparent  that  seams  in  the  wire  that  do 
not  appear  to  be  of  sufficient  depth  to  give  trouble  may  become 
very  objectionable  because  of  the  tendency  to  deepen  during 
the  conversion  of  the  stock  into  ball  blanks.  Upset  disk  B 
is  of  about  the  same  diameter  as  a  ball  blank  made  from  this 
wire  by  the  cold-heading  process,  so  that  it  has  been  subjected 
to  about  the  same  amount  of  stretch  in  upsetting  that  would 
ordinarily  take  place  in  making  a  ball  blank  by  the  cold-heading 
process.  To  show  how  trouble  may  develop  in  this  way,  a 
ball  0.375-inch  in  diameter  is  produced  from  a  blank  0.400 
inch  in  diameter,  so  that  the  blank  is  reduced  0.025-inch  on 
the  diameter,  or  approximately  0.013-inch  on  the  radius.  This 
leaves  0.050  minus  0.013,  or  0.037-inch  of  the  split  extending 
below  the  surface  of  the  finished  ball,  which  will  certainly  lead 
to  its  rejection  by  the  inspectors. 

It  appears  that  hardness  of  the  wire  does  not  cause  splitting 
of  the  upset  blank.  Tests  conducted  with  a  view  to  establish- 
ing this  fact  have  shown  that  blanks  made  from  seamless  steel 


57 


Fig.   34.     Photomicrographs   of  Sections   on   Lines   a-b   and   c-d   in   Fig.   33, 
indicating  Increase  in  Size  of  Seam   through  stretching  of 
Metal     Surface     in     Upsetting. 


with  a  high  Brinell  hardness  number  did  not  split  under  the 
most  severe  conditions  of  upsetting,  while  blanks  of  metal 
with  a  low  Brinell  hardness  number,  but  with  seams  on  their 
surfaces,  were  frequently  split  during  the  process  of  cold-heading. 
Specifications  under  which  steel  is  purchased  for  the  production 
of  ball  blanks  in  cold-heading  machines  call  for  metal  with 
a  hardness  number  not  exceeding  170  as  determined  by  the 
Brinell  method,  but  slightly  harder  stock  is  capable  of  being 
worked  with  fairly  satisfactory  results. 

HOW  SEAMY  STOCK  ACTS  IN 
COLD-HEADING  MACHINE 

IN  ORDER  to  confirm  the  accuracy  of  the  conclusions  reached 
in  regard  to  the  action  of  seamy  stock  when  worked  up  into 
ball  blanks  in  the  cold-heading  machines,  tests  were 
conducted  by  placing  coils  that  had  bad  seams  in  them  on  the 
cold-headers  and  observing  the  kind  of  ball  blanks  that  were 
produced.  In  every  case  it  was  found  that  the  blanks  produced 
from  such  stock  showed  bad  cracks,  as  shown  at  A  in  Fig.  35. 
In  the  inspection  department,  cracks  found  in  finished  balls 
were  at  one  time  commonly  referred  to  as  "fire  cracks"  on  the 
assumption  that  they  were  developed  during  the  process  of  heat- 
treatment,  but  they  are  now  designated  as  ' 'header  cracks."  In 


58 


this  illustration  attention  is  called  to  the  fact  that  at  the  top 
and  bottom  of  each  ball  blank  there  is  a  small  projection  formed 
by  pressing  the  metal  into  the  knock-out  pin  hole  in  the  header 
dies.  These  have  been  termed  ' "poles,"  and  it  will  be  noted 
that  the  poles  lie  on  the  axis  of  the  wire.  Midway  between 
the  two  poles  there  is  a  band  or  "fin"  caused  by  the  metal  being 
forced  out  between  the  two  header  dies;  and  this  fin  has  been 
termed  the  "equator"  of  the  ball. 


Fig.   35.      (A)    Cold- header   Ball   Blanks,   showing   Splits   running   from  Pole 

to  Pole,   (B)   Finished  Balls  produced  from  Blanks  Split  during 

Cold- heading  Operation. 


It  will  be  noted  at  A  in  Fig.  35  that  the  header  cracks  run 
from  pole  to  pole.  At  B  in  the  same  illustration  are  shown 
some  finished  balls  with  the  same  kind  of  cracks,  and  it  has 
always  been  found  that  cracks  in  the  finished  balls  have  been 
lengthened  to  a  considerable  extent,  the  ends  of  these  cracks 
terminating  in  very  fine  lines.  This  can  be  readily  understood 
when  we  consider  that  a  small  crack  or  fine  sharp  tool  mark  on  a 
piece  to  be  hardened  causes  a  weak  spot  which  in  many  cases 
will  result  in  splitting  the  piece  during  the  process  of  heat- 
treatment.  At  A  in  Fig.  36  are  shown  some  balls  that  were 
picked  out  in  the  inspection  department  because  they  had  fire 
cracks;  these  were  sent  to  the  laboratory  and  fractured  to 
reveal  the  grain  of  the  metal.  It  will  be  noticed — particularly 
in  the  third  ball  of  the  third  line — that  at  the  extreme  left  of 
the  fracture  there  is  a  dark  spot  near  the  surface,  which  is 


59 


the  mark  left  by  the  original  crack  produced  during  the  cold- 
heading  operation.  Then  to  the  extreme  right  there  is  a 
fresh  fracture  which  represents  all  the  metal  that  the  ball  had 
to  hold  it  together  after  being  hardened. 

Attention  is  called  to  the  fact  that  the  middle  of  the  ball  is 
black  and  oily;  this  is  the  hardening  crack  into  which  the  oil 
and  abrasive  have  found  their  way  during  the  oil-rolling  and 


rveo 


Fig.  36.      (A)   Fractures  of  Balls  shown  at   (B)    in  Fig.  35,  showing   Original 

Header  Crack,  Fire  Crack  and  Fracture  of  Uncracked  Metal,  (B)  Etched 

Balls,  showing  Crack  from  Pole  to  Pole  and  Crack  on  Equator. 


grinding  operations.  The  crack  produced  in  cold-heading  was 
the  cause  of  a  further  cracking  of  the  ball  during  the  process 
of  heat-treatment.  At  B  in  Fig.  36  are  shown  some  finished 
balls  that  were  rejected  by  the  inspectors  because  of  cracks. 
Before  being  photographed  these  balls  were  etched  with  dilute 
hydrochloric  acid,  and  it  will  be  noticed  that  the  cracks  run 
from  pole  to  pole,  and  in  some  cases  there  are  also  secondary 
cracks  following  the  line  of  the  equator.  The  way  in  which 
these  equatorial  cracks  are  produced  can  best  be  explained  by 
reference  to  Fig.  37.  At  A  is  shown  a  longitudinal  section  of 
the  wire  which  has  been  etched  with  hydrochloric  acid  to 
reveal  the  structure  of  the  metal.  Attention  is  called  to  the 
lamellar  structure,  which  is  characteristic  of  any  steel  and  is  no 
reflection  upon  its  quality.  These  laminations  run  lengthwise  of 
the  coil.  At  B  is  shown  a  section  of  a  headed  ball  blank  made 
from  a  piece  of  this  wire  and  etched  with  acid  to  bring  up  the 


60 


Fig.  37.  (A)  Section  of  Steel  Stock,  showing  Lamellar  Structure;  (B)  Cross- 
section  of  Cold-header  Ball  Blank,  showing  Distortion  of  Steel  Structure;  (C) 
Cross-section  of  Header  Cracked  Ball  Blank;  (D)  Ball  Blank  shown  in  Cross- 
Section  at  (C);  (E)  Cold-header  Ball  Blank  with  Large  Fin;  (F)  Perfect  Cold- 
header  Ball  Blank;  (G)  Etched  Ball,  showing  End  Grain  of  Steel  at  Equator; 
(H)  Etched  Ball,  showing  End  Grain  of  Steel  at  Pole. 


structure  of  the  metal.  Here  it  will  be  seen  that  the  lamina- 
tions have  arranged  themselves  in  a  manner  similar  to  magnetic 
lines  of  force  running  from  pole  to  pole. 

At  D  and  E  are  shown  header-cracked  ball  blanks,  and  it 
will  be  noticed  that  blank  E  shows  an  unusually  large  fin  on 
one  side.  Blank  D  shows  the  split  on  one  side  and  also  a  por- 
tion of  the  split  extending  into  the  fin.  Blank  F  is  properly 
headed  and  shows  no  crack  or  excessively  large  fins.  Referring 
to  the  view  shown  at  C,  which  is  a  cross-section  of  blank  D, 
it  will  be  seen  that  the  split  extends  into  the  fin,  and  it  will 
also  be  noted  that  the  crack  extends  below  the  surface  of  the  ball, 
although  it  comes  to  the  surface  at  each  end  at  points  near 
the  poles.  This  is  due  to  the  fact  that  the  split  does  not  penetrate 
the  ball  at  right  angles  to  the  surface,  but  runs  on  a  slant.  Instead 
of  compressing  and  filling  up  the  open  space  in  the  ball,  material 
has  been  pressed  outward  and  made  a  large  fin;  when  this  fin 


61 


is  ground  away,  the  crack  is  quite  evident.  At  G  and  H  are 
shown  finished  balls  that  have  been  etched  with  acid  to  show  the 
grain  at  the  equator  and  at  the  poles,  respectively. 


HEADED  BLANK 


FINISHED  BALL 


Fig.  38.     Diagram  illustrating  Distortion  of  Steel  Structure  in  Cold-header 
Ball  Blank  similar  to  that  shown  at  (B)  in  Fig.  37. 


Referring  again  to  the  sectional  view  of  the  wire  shown 
at  A  in  Fig.  37,  and  also  to  the  cross-section  of  a  ball  blank 
made  from  this  wire  shown  at  B,  it  will  be  seen  that  the  structure 
of  the  steel  has  been  greatly  disturbed  during  the  process  of 
cold-heading  to  produce  the  ball  blank.  In  Fig.  38  is  shown 
diagrammatically  the  way  in  which  this  disturbance  takes 
place.  It  will  be  seen  that  the  ends  of  the  fibers  come  to  the 
surface  at  the  poles  and  at  both  sides  of  the  equatorial  fin; 
and  when  the  ball  is  etched  the  steel  is  attacked  more  rapidly 
at  these  points.  The  peculiar  marks  shown  at  G  and  H  in  Fig.  37 
are  the  result  of  this  disturbance  of  structure.  The  conclusion  has 
been  reached  that  when  a  ball  with  so-called  ' 'header  cracks"  is 
etched  with  acid  and  shows  two  end  poles  and  two  equatorial  marks 
with  a  wide  crack  running  from  pole  to  pole  or  possibly  a  secondary 
crack  running  between  the  two  equators,  this  crack  is  a  header 
crack  which  is  caused  by  a  seam  or  lap  in  the  steel  from  which 
the  ball  was  made.  The  internal  stress  due  to  the  structural 
distortion  illustrated  in  Fig.  38  is  completely  normalized  by  the 


annealing  treatment  to  which  all  Hoover  balls  are  subjected. 
A  number  of  these  headed  balls  with  header  cracks  were 
heated  in  an  electric  furnace  in  the  laboratory  and  quenched 
in  water  at  1500  degrees  F. ;  every  ball  was  further  cracked  by 
this  treatment,  and  several  of  them  fell  in  half  or  were  easily 
broken  by  a  light  hammer  blow.  Another  lot  of  headed  balls 
with  no  header  cracks  was  heated  in  the  electric  furnace  and 
quenched  in  water  at  1600  degrees  F.,  and  not  a  ball  was  cracked 
in  hardening.  Balls  quenched  in  water  at  1500  degrees  F.  that 
broke  during  the  process  of  heat-treatment  are  shown  at  A  in  Fig. 
39,  while  the  balls  quenched  in  water  at  1600  degrees  F.,  without 
damage  are  shown  at B  in  the  same  illustration.  At  this  excessive 
temperature  the  grain  of  the  metal  was  coarsened,  but  no  hard- 
ening cracks  were  produced  and  it  required  considerable  force 
to  break  the  balls.  Several  finished  balls  were  next  selected 
in  the  inspection  department  that  showed  very  slight  header 
cracks.  These  balls  were  hardened  at  1500  degrees  F.  and  cracked 
in  the  process  of  hardening  exactly  as  before.  The  characteristic 
black  mark  left  by  the  original  header  crack  is  shown  at  one  side 
of  the  balls  at  C  in  Fig.  39.  Another  lot  of  finished  balls  showing 
no  header  cracks  was  hardened  at  1600  degrees  F.  and  none 
of  the  balls  was  cracked,  views  of  the  fractured  surfaces  of  these 
balls  being  shown  at  D  in  Fig.  39.  This  confirmed  the  accuracy 
of  previous  tests,  and  from  these  data  the  following  conclusions 
were  drawn:  (1)  The  header  crack  forms  a  weak  spot,  so  that 
when  the  ball  is  hardened,  even  at  the  proper  temperature, 


•••• 

?••  •  •• 


••• 


Fig.  39.  (A)  Fractures  of  Header  Cracked  Balls  that  Split  when  re-heat-treated 
in  Laboratory  at  1500  Degrees  F.,  (B)  Fractures  of  Perfect  Balls  that  did  not 
Split  when  re-heat-treated  at  1600  Degrees  F.;  (C)  Fractures  of  Balls  with 
Slight  Cracks  which  broke  when  re- heat-treated  at  1500  Degrees  F.,  (D) 
Fractures  of  Perfect  Balls  that  did  not  break  when  re- heat-treated  at  1600 

Degrees  F. 


63 


what  the  inspectors  call  a  "fire  crack"  is  likely  to  be  produced. 
(2)  A  ball  with  no  header  cracks  can  be  hardened  at  an  excessively 
high  temperature  without  producing  a  fire  crack. 

Another  hardening  test  was  made  with  four  samples  of  wire, 
two  pieces  of  which  showed  seams,  and  two  pieces  that  did  not. 
The  seamy  pieces  of  wire  were  quenched  at  a  temperature  of 
about  1500  degrees  F.  in  water  and  hardening  cracks  developed 
along  the  seams.  The  two  pieces  without  seams  were  quenched 
in  water  at  a  temperature  of  1600  degrees  F.  and  no  cracks 
developed.  All  these  tests  show  that  with  small  blanks  with- 
out any  header  cracks,  it  is  practically  impossible  to  produce 
fire  cracks  in  the  automatic  hardening  furnaces;  when  cracks 
are  produced  they  are  started  in  cold-heading  and  not  through 
the  process  of  heat-treatment.  The  shape  of  the  ball  is  in  its 
favor,  as  it  insures  uniform  quenching  and  a  minimum  of  internal 
strain.  Application  of  too  high  a  temperature  would  tend  to 
increase  the  size  of  the  grain  in  the  steel  and  make  it  brittle 
and  unfit  for  use,  but  it  would  not  produce  hardening  cracks. 

EFFECT  OF  HARDNESS 
OF  WIRE 

WHEN  the  wire  used  in  making  ball  blanks  on  cold-headers 
is  too  hard,  there  is  a  tendency  for  it  to  break  off  instead 
of  shearing  as  it  should.  When  trouble  of  this  sort  is 
encountered,  it  is  likely  to  be  accentuated  by  the  fact  that  the 
blank  is  often  carried  to  the  heading  die  in  a  sidewise  position, 
which  results  in  the  development  of  abnormal  pressure  in  the 
die.  Working  hard  stock  of  this  kind  results  in  breaking  the 
cut-off  knife  or  the  dies  on  the  cold-heading  machine.  This 
condition  of  excessive  hardness  does  not  usually  exist  for 
the  entire  length  of  the  coil ;  wire  may  shear  off  and  head  nicely 
for  some  time,  when  suddenly  a  hard  spot  will  be  reached  and 
then  the  dies  or  the  cut-off  knife  is  likely  to  suffer.  After  this 
hard  spot  has  been  passed,  the  wire  may  be  all  right  for  another 
period  of  considerable  duration.  With  the  view  of  showing 
the  relative  condition  of  hard  and  soft  spots  in  the  wire,  slugs 
of  metal  were  selected  at  a  point  where  trouble  was  encountered 
from  this  cause,  and  again  at  a  point  where  the  operation  of 
the  cold-header  was  entirely  satisfactory.  These  were  tested 


64 


Fig.  40.  (A)  Fracture  of  Hard  Metal  Slug;  (B)  Fracture  of  Normal  Metal  Slug; 

(C)   Etched  Surface  of  Hard  Steel   magnified  5.25   Diameters— Attention   is 

called  to  Decarbonization  at  Circumference;  (D)  Etched  Surface  of  Normal 

Steel   with   No   Decarbonization   at    Circumference. 


by  the  Brinell  method  and  it  was  found  that  the  hard  slugs 
had  a  Brinell  hardness  number  of  215,  while  the  soft  slugs  only 
showed  a  Brinell  hardness  number  of  190.  The  latter  is  really 
higher  than  it  should  be,  as  170  is  specified  for  steel  to  be  used  in 
cold-heading  machines. 


"Fig.  41.    (A)  Decarbonized  Surface  shown  at  (C)  in  Fig.  40  magnified  to  Sixty- 
two   Diameters;    (B)    Same   Magnification   as   at    (A),   showing    Condition   of 
Practically  No  Decarbonization. 


65 


At  A  in  Fig.  40  is  shown  the  fresh  fracture  of  a  slug  of  hard 
metal  and  attention  is  called  to  the  coarse  grain  as  compared 
with  the  finer  grain  of  the  normal  steel  shown  at  B.  The  hard 
specimen  was  very  brittle  and  easy  to  break,  while  the  normal 
steel  was  tough  and  capable  of  bending  considerably  before 
being  broken.  Specimens  of  these  two  steels  were  next  polished 
and  etched,  with  the  result  shown  at  C  and  D,  respectively. 
These  are  transverse  sections  cut  through  the  wire,  and  attention 
is  called  to  the  coarse  grain  of  the  steel  shown  at  C\  the  ring  at  the 
surface  is  a  band  of  decarbonized  steel  apparently  produced  by 
the  application  of  too  high  an  annealing  temperature.  The 
normal  steel  shown  at  D  has  a  fine  grain  and  there  is  no 
indication  of  decarbonization. 

At  A  in  Fig.  41  is  shown  the  decarbonized  band  of  steel  sur- 
rounding section  C  in  Fig.  40,  which  is  magnified  to  62  diameters, 
instead  of  5.25  diameters,  as  in  the  case  of  the  previous  illustra- 
tion. It  will  be  noted  that  the  extreme  edge  of  this  photomicro- 
graph is  somewhat  indistinct,  owing  to  the  slightly  rounded 
edge  formed  while  polishing  the  specimen.  The  decarbonized 
surface  of  this  stock  would  not  be  entirely  removed  in  the  process 
of  grinding,  and  would  result 'in  the  production  of  either  soft 
balls  or  balls  with  soft  spots.  AtB,  Fig.  41,  we  have  the  condition 
where  there  is  practically  no  loss  of  carbon  at  the  surface. 
At  A  and  B  in  Fig.  42  is  seen  a  decided  contrast  between  the 


Fig.  42.     (A)  Pronounced  Pearlitic  Structure  with  large  cells  and  Boundaries 
of  excess  Cementite,  indicating  Application  of  too  High  an  Annealing  Temper- 
ature; (B)  Fine-grained  Structure,  showing  Condition  obtained  with  Proper 
Annealing    Temperature.      Both   Samples    magnified    to   225    Diameters. 


66 


structure  of  the  slug  of  hard  metal  and  that  taken  from  the 
normal  wire.  At  A  there  is  a  pronounced  pearlitic  structure 
with  large  cells  and  distinct  boundaries  of  excess  cementite, 
which  also  indicates  the  application  of  too  high  an  annealing 
temperature.  At  B  the  structure  is  fine  grained,  which  is  the 
condition  produced  by  employing  the  proper  annealing 
temperature.  Where  lack  of  uniformity  is  discovered  in 
the  hardness  of  the  wire,  it  is  probably  due  to  application  of  too 
high  an  annealing  temperature. 

CAUSE  OF  SOFT  SPOTS 
ON  BALLS 

SOME  valuable  discoveries  have  been  made  in  the  laboratory 
as  a  result  of  work  that  was  started  with  some  other  object 
in  view.  For  instance,  an  investigation  that  was  started 
with  the  view  of  determining  the  effect  of  slight  seams  found  in 
a  certain  shipment  of  steel  at  the  time  of  the  preliminary  tests. 
These  seams  were  not  considered  serious  enough  to  justify  rejec- 
tion of  the  steel,  but  after  the  first  lot  of  blanks  had  been  finish 
dry  ground,  tests  were  made.  This  was  done  by  etching  a  number 
of  balls  in  dilute  hydrochloric  acid,  to  see  if  the  seams  had  been 
removed  in  grinding.  The  balls  were  immersed  in  the  solution, 
and  after  being  etched  for  fifteen  or  twenty  minutes  they  were 
removed,  and  cleaned. 

When  treated  in  this  way,  the  balls  are  usually  a  light  gray 
color  over  their  entire  surface,  but  the  particular  lot  of  balls 
referred  to  could  not  be  uniformly  etched.  At  first  it  was  thought 
that  a  film  of  grease  or  some  other  foreign  matter  was  interfering 
with  the  action  of  the  acid,  but  a  second  trial  resulted  in  the 
same  mottled  appearance  of  the  etched  balls.  Part  of  the  surface 
was  light  gray,  while  other  parts  were  dark  gray  and  almost  black. 
Balls  with  these  spots  are  shown  in  Fig.  43  and  no  matter  how 
often  they  were  re-etched,  the  same  spots  always  appeared  and 
they  were  of  the  same  outline  as  those  developed  by  the  pre- 
vious etching.  Some  of  the  unetched  samples  were  examined, 
and  it  was  found  that  a  considerable  quantity  of  black  scale 
was  left  on  the  balls,  i.  e.,  the  forging  had  not  been  cleaned 
up  properly  after  the  finish  dry-grinding.  At  this  stage  the  ball 


67 


Fig.  43.    Finish  Dry-ground  Balls  after  being  etched  with  Hydrochloric  Acid, 
showing  Mottled  Appearance  due  to  Soft  Spots  produced  by  Decarbonization 

of  Steel. 


consistently  measured  1.135  inch,  i.  e.,  within  0.010  inch  of  the 
finished  size — -\Y%  inch. 

Thus  far  results  seemed  to  indicate  that  the  forging  blanks 
were  under  size,  so  five  samples  were  selected  at  random  and 
measured.  The  measurements  of  these  five  blanks  are  given 
in  Table  4,  reference  to  which  will  show  that  dimensions  A  across 
the  poles  and  dimension  B  near  the  poles  were  of  ample  size; 
and  the  surfaces  at  or  close  to  the  poles  were  also  smooth  and 
well  filled  out.  However,  these  conditions  did  not  exist  around 
the  equator,  where  it  will  be  seen  that  dimension  C  was  scant 
in  many  balls,  and  additional  trouble  was  caused  by  the  fact 
that  the  surface  was  very  rough  and  covered  with  "hills"  and 
' Valleys."  In  making  these  equatorial  measurements  with  a 
micrometer,  the  distance  is  taken  across  the  tops  of  the  ' 'hills," 
while  the  dimensions  in  the  'Valleys"  will  obviously  be  consider- 
ably less.  It  is  doubtful,  therefore,  whether  three  out  of  five  of 


68 


these  samples  would  clean  up  in  the  rough  dry-grinding.  A 
re-examination  of  the  etched  dry-ground  balls  showed  that  the 
peculiar  black  spots  did  not  appear  at  the  poles  as  frequently 
as  they  did  at  the  equator;  and  when  a  new  file  was  applied  to 
the  black  spots  shown  in  Fig.  43,  it  was  found  that  they  were 
dead  soft,  while  the  light  gray  spots  were  very  hard.  The 
sclerescope  hardness  of  ten  of  these  balls  was  taken  and  averaged 
as  follows:  black  spots,  48;  gray  spots,  70. 

Table  IV.    Measurements  of  Balls  across  Poles,  near 
Poles  and  at  Equator. 


1.168 
1.169 
1.170 


1.166 
1.161 
1.151 
1.175 
1.152 


1.161 
1.167 
1.145 
1.172 
1.170 


1.160 
1.163 
1.145 
1.170 
1.158 


1.166 
.162 
.150 
.159 

.167 


The  reason  for  these  spots  will  be  understood  from  the 
photomicrographs  presented  at  A  and  B  in  Fig.  44,  which  are 
taken  from  polished  surfaces  at  the  extreme  outer  surface  of 
the  black  and  white  spots  on  the  balls.  These  surfaces  were 
prepared  and  photographed  in  exactly  the  same  way;  instead 
of  polishing  a  flat  on  the  ball,  the  spherical  surface  was  polished, 
because  a  flat  surface  having  any  width  whatever  would  also 
be  at  a  considerable  depth  below  the  surface  of  the  ball,  and 
would  not  reveal  conditions  that  it  was  desired  to  investigate. 
Difficulty  was  experienced  in  polishing  this  spherical  surface, 
and  so  the  photographs  reproduced  in  Fig.  44  show  polish  marks 
rather  too  distinctly,  but  these  have  no  bearing  upon  the  accuracy 
of  the  results  obtained  in  the  investigation.  At  A  is  shown  a 
large  percentage  of  free  ferrite,  indicating  a  hypo-eutectoid 
structure  of  about  0.30  to  0.40  per  cent  carbon;  in  other  words, 
the  metal  is  similar  to  a  mild  steel.  On  the  other  hand,  the 
condition  revealed  at  B  is  practically  a  pure  eutectoid  structure 
of  pearlite,  this  steel  having  from  0.85  to  0.90  per  cent  carbon. 
Specifications  under  which  the  steel  is  purchased  call  for  from 
0.95  to  1.05  per  cent  of  carbon,  so  that  in  this  regard  it  fulfills 
requirements. 


69 


Fig.  44.     (A)  Photomicrograph  of  Black  Soft  Spots  on  Balls  shown  in  Fig.  43, 

showing  Large  Percentage  of  Free  Ferrite  or  Hypo-eutectoid  Structure;   (B) 

Photomicrograph  of  Hard  White  Spots  on  Balls  shown  in  Fig,  43,  indicating 

the  Desired  Eutectoid  Structure. 


A  further  test  was  conducted  by  preparing  flat  surfaces  of 
considerable  depth  on  the  balls  and  examining  these  under  the 
microscope;  and  in  both  cases  it  was  found  that  photomicro- 
graphs obtained  in  this  way  indicated  metal  containing  its  full 
percentage  of  carbon.  Hardness  tests  show  that  the  metal 
directly  under  the  decarbonized  spot  is  soft  and  indicate 
not  only  that  the  decarbonized  surface  fails  to  harden,  but  that 
it  also  forms  a  sort  of  insulator  and  retards  the  proper 
hardening  of  the  eutectoid  steel  beneath  it.  Therefore,  the 
decarbonization  plus  its  effects  means  a  soft  area  of  decided 
depth,  so  deep,  in  fact,  that  when  the  ball  is  finished  the 
soft  spot  still  appears.  Having  reached  this  conclusion,  specimens 
of  the  raw  material  were  prepared  by  cutting  sections  trans- 
versely from  the  bar,  and  these  were  prepared  and  photographed 
Fig.  45  illustrating  the  conditions  that  were  revealed  in  this  way. 
It  will  be  noted  that  the  steel  shown  at  A  is  decarbonized  to  a 
depth  of  0.010  inch — 0.020  inch  on  the  diameter  of  the  ball- 
while  in  the  sample  shown  at  B  there  is  no  decarbonization.  It 
was  this  steel  with  the  decarbonized  surface  that  produced  balls 
showing  soft  spots  in  the  tests. 

Fifty  of  these  balls  showing  soft  spots  were  taken  to  the 
laboratory,  where  they  were  again  heat-treated,  and  the  result 
was  that  the  balls  came  out  hard.  It  was  not  considered,  how- 
ever, that  this  indicated  defective  heat-treatment  in  the  process 


70 


Fig.  45.  (A)  Photomicrograph  of  Transverse  Section  of  Decarbonized  Edge  of 
Steel — Magnification,  125  Diameters;  (B)  Photomicrograph  of  Transverse 
Section  of  Steel  showing  No  Decarbonization — Magnification,  125  Diameters. 


of  manufacture,  because  it  might  have  happened  that  the 
operation  of  finish  dry-grinding  removed  enough  metal  from 
the  surface  so  that  the  balls  would  harden  properly,  although 
they  were  prevented  from  doing  so  at  the  time  of  the  original 
treatment  by  the  decarbonized  steel  that  covered  the  surface 
of  the  balls.  Because  of  the  oval  shape  of  the  forgings,  the  depth 
of  decarbonization  varies  at  different  spots  on  the  rough-ground 
surface  of  the  balls;  for  example,  at  the  poles  there  is  little  or  no 
decarbonization,  while  around  the  equator  the  decarbonization 
is  quite  deep.  When  a  ball  is  reduced  to  the  finished  size,  the 
following  conditions  will  be  found :  (1)  decarbonized  areas  where 
the  original  decarbonization  on  the  rough  ball  was  deep;  (2) 
soft  areas  where  the  original  decarbonization  on  the  rough  ball 
was  shallow;  (3)  hard  areas  where  there  was  little  or  no  de- 
carbonization  on  the  rough  ball.  In  cases  (2)  and  (3)  the  steel 
has  its  full  percentage  of  carbon,  and  when  the  balls  are  rehard- 
ened  some  of  the  soft  spots  disappear,  while  the  spots  devoid 
of  carbon  still  remain  soft.  It  would  be  possible  to  reduce  these 
balls  to  a  smaller  size  and  reclaim  them  by  rehardening,  but  this 
subsequent  heat-treatment  has  a  tendency  to  roughen  their 
surface  slightly,  which  necessitates  subsequent  grinding  opera- 
tions jhat  would  probably  reduce  the  diameter  from  0.015 
to  0.020  inch,  so  that  allowance  must  be  made  for  this 
reduction  in  size. 


71 


To  overcome  trouble  from  the  use  of  stock  that  is  decarbon- 
ized at  the  surface,  special  forging  dies  were  made  which  produce 
oversize  ball  blanks,  so  that  the  diameter  at  the  equator  measures 
from  0.060  to  0.080  inch  more  than  that  of  the  standard  finished 
balls.  The  same  stock  forged  in  a  regular  die  would  make  a 
blank  0.025  inch  to  0.035  inch  larger  than  the  finished  size.  In 
the  present  case  it  is  found  that  these  would  not  clean  up,  but 
left  soft  and  decarbonized  spots  on  the  surface  of  the  finished 
ball.  For  this  reason,  the  special  forging  dies  were  produced. 
This  practice  was  adopted  because,  owing  to  the  slow  deliveries 
made  by  the  steel  mills,  it  was  desired  not  to  reject  any  steel  of 
this  size  that  could  possibly  be  used. 

DEVELOPMENT  OF  A  DEVICE  FOR 
SEPARATING  HARD  AND  SOFT  BALLS 

OWING  to  shipment  to  the  factory  of  a  large  quantity  of 
low  carbon  steel  through  an  error  made  at  the  steel  mills, 
and  which  escaped  the  rigid  sampling  to  which  every 
car  of  steel  received  at  the  Hoover  plant  is  subject,  about 
seven  tons  of  this  material  was  converted  into  ball  blanks 
before  it  was  attempted  to  harden  them.  This  was  due  to 
the  fact  that  a  large  supply  of  blanks  of  the  same  sizes 
had  accumulated,  and  these  were  naturally  sent  through  the 
heat-treating  department  ahead  of  blanks  made  from  this 
shipment  of  steel.  When  the  blanks  had  been  heat-treated,  they 
were  tested  in  order  to  determine  the  nature  of  the  results 
obtained,  and  while  a  number  of  balls  broke  with  a  fine-grained 
fracture  and  showed  a  hardness  that  was  all  that  could  be  desired, 
almost  10  per  cent  of  the  balls  were  found  to  be  dead  soft.  When 
these  balls  were  subjected  to  pressure  they  flattened  out  instead 
of  breaking  in  the  usual  way.  A  peculiar  mottled  effect  was 
noted  on  the  balls  found  to  be  file  hard,  while  the  soft  balls 
were  a  dull  black  color ;  but  this  difference  in  appearance  was  not 
sufficiently  marked  to  enable  the  balls  to  be  separated,  and  even 
had  this  been  possible,  the  length  of  time  required  to  eliminate 
defective  balls  by  this  method  would  have  been  prohibitive. 
With  a  view  to  overcoming  this  difficulty,  a  device  was  de- 
veloped which  is  shown  in  diagrammatic  form  in  Fig.  46.  Its 
principle  of  operation  is  based  on  the  fact  that  when  balls  are 


dropped  on  a  hardened  steel  anvil  there  is  considerable  difference 
in  the  height  of  the  rebound  of  hard  and  soft  balls.  The  balls 
to  be  tested  roll  down  an  incline  plane  and  drop  upon  a  hardened 
steel  block,  from  which  they  rebound;  the  hard  balls  rise  high 
enough  to  pass  over  a  "hurdle"  into  a  box,  while  the  soft  balls 
do  not  reach  this  height  and  are  deposited  in  a  second  box.  To 
test  the  efficiency  of  this  device,  119  balls  taken  from  one  of  the 
tote  pans  in  the  shop  were  run  through  the  drop  test;  79  dropped 
into  the  "hard  bin"  and  40  into  the  "soft  bin."  These  balls  were 
once  more  thoroughly  mixed  and  again  run  through  the  ap- 
paratus with  the  same  result  as  in  the  previous  case.  Additional 
trials  confirmed  the  accuracy  of  the  apparatus.  This  method  of 
separation  proved  so  satisfactory  that  a  regular  equipment 
has  been  built  for  use  in  the  dry-grinding  room,  where  it  is 
used  for  separating  hard  and  soft  balls. 


/   ! 

1 

HARD           O 
BALLS          ,f: 

"ji^lr 

ZT\     47"    i— 

_,__47           .4               >, 

-t—  -„   \ 

i                   S&          /                        <**' 
3lW                  x  \     t 

SOFT- 
BALLS 

\\   / 

X 

y§n&sj 

HARD 

A                            ANVIL"                                               | 

Fig.  46.     Diagram  illustrating  Principle  of  Apparatus  developed  for 
Automatic  Separation  of  %-inch  Hard  and  Soft  Balls. 


CONCLUSION 

MANY  of  the  cases  of  trouble  to  which  reference  has  been 
made  are  of  rare  occurrence,  but  it  is  obvious  that  they 
exert  a  powerful  influence  on  the  quality  of  the  product 
turned  out  in  the  factory.    Also,  the  conditions  brought  to  light 
by  these  investigations  are  exceptionally  interesting.     It  was  on 


73 


this  account  that  they  were  selected  for  discussion  in  the  present 
treatise,  in  connection  with  the  regular  work  of  the  laboratory, 
and  not  because  they  really  belong  to  a  description  of  routine 
work  of  testing  the  raw  material  and  product  of  a  factory  en- 
gaged in  the  manufacture  of  steel  balls. 


CRUSHING  AND  DEFORMATION 
TESTS 

THE  old  method  of  determining  the  crushing  load  of  a 
ball  was  to  test  a  single  ball  between  two  hardened  steel 
plates.    It  is  obvious  that  if  the  plates  were  not  of  uniform 
hardness  the  crushing  loads  would  also  lack  uniformity,  because 
the  plates  would  be  indented  during  the  test  and  the  softer  plate, 
being  indented  the  greater,  would  present  more  supporting  area 
to   the   ball,   and   thereby  increase  its   resistance   to   crushing. 
Inability   to   produce   plates  of  absolute   uniformity   puts   this 
method  out  of  the  question  as  a  standard  test. 

The  Hoover  Steel  Ball  Co.  has  developed  the  Three-Ball 
test  as  a  standard.  Three  balls  super-imposed,  as  shown  in 
the  illustration,  are  subjected  to  a  gradually  increasing  pressure 
until  rupture  occurs,  and  the  amount  of  pressure  is  recorded  at 
this  point. 

We  wish  to  emphasize  that  testing  by  the  Three-Ball  method 
will  yield  results  somewhat  lower  than  by  the  plate  test  by 
reason  of  the  fact  that  the  contact  points  are  very  minute  and 
therefore  the  pressure  per  unit  of  area  is  tremendous. 

The  plate  test  is  very  often  used  by  some  ball  manufacturers 
to  deceive  the  buyer  by  making  him  believe  he  is  getting  a  better 
ball  by  reason  of  the  high  crushing  load. 

Believing  that  a  table  of  crushing  loads  would  be  of  very 
little  value  to  our  customers,  as  a  guide  to  determine  the  safe 
working  load  of  the  ball,  and  that  such  a  table  might  be  mislead- 
ing, we  refrain  from  publishing  same. 

It  is  evident  that  the  safe  working  load  that  a  ball  will 
carry  depends  not  only  upon  the  quality  of  the  ball,  but  also 
upon  the  type  of  bearing  in  which  it  is  to  run,  the  shape,  material 
and  finish  of  the  ball  race,  etc. 


74 


We  stand  ready  at  all  times,  however,  to  give  our  customers 
information  as  to  crushing  strength  and  elastic  strength,  and 
to  give  our  opinion  as  to  the  most  suitable  size  and  type  of 
ball  for  any  particular  work,  after  we  have  received  full  particulars 
of  the  bearing  and  the  nature  of  the  work  for  which  it  is  required, 
load,  speed,  etc. 


Ball  Crushing  Apparatus 


75 


76 


I 
I 

I* 


Is 


Cft; 
Sfe 

ii 


77 


78 


Fracture  of  a  hard  surface  tough  center  ball.     Note  the  flattening  and  cone  of  rupture  at  the  points 
of  contact,  formed  when  the  balls  were  crushed. 


HOOVER  STEEL  BALLS  HAVE  A  HARD 
SURFACE  AND  A  TOUGH  CENTRE 

CO-OPERATION  with  our  customers  and  extensive  service 
tests  of  our  balls  have  developed  a  method  of  heat 
treatment  which  while  simple  in  its  theory  is  difficult  of 
practical  control,  and  this  control  is  only  made  possible  by 
automatic  hardening  machines  which  eliminate  the  personal 
element. 

It  is  not  a  difficult  matter  to  harden  a  ball  clear  through 
to  the  centre,  as  it  is  merely  a  question  of  quenching  at  a  tempera- 
ture sufficiently  high  to  harden  the  interior,  but  this  method  is 
without  due  regard  to  the  exterior.  Hardening  a  ball  under 
these  conditions  produces  an  over-heated  exterior  which  is 
necessarily  brittle,  and  strength  cannot  be  restored  by  tempering. 

Hoover  balls  are  heat-treated  to  produce  a  sufficiently 
hard  exterior  and  a  tough  semi-hard  interior,  producing  the 
qualities  most  needed  in  ball  bearings.  The  surface  is  sufficiently 
hard  to  withstand  wear,  without  being  so  brittle  as  to  flake  or 
peel.  The  interior  is  sufficiently  tough  and  elastic  to  stand  the 
strain  of  heavy  loads. 

This  type  of  ball  must  not  be  confused  with  a  low  grade 
steel  ball  "case  hardened"  on  the  surface  and  with  a  soft  core. 

When  we  speak  of  hard  surface  and  tough  centre  we  refer 
to  a  high  grade  alloy  steel  in  which  there  is  a  gradual  merging 
of  hardness  at  the  surface  to  semi-hardness  at  the  core,  without 
a  distinct  line  of  demarkation  as  in  the  "case  hardened"  ball. 

The  above  photograph  shows  the  fracture  of  a  hard  surface* 
tough  centre  ball,  of  which  the  Hoover  Steel  Ball  Co.  is  the 
exponent. 


SMOOTH  AND  MIRROR-LIKE  surface  finish  must  be  maintained  in  every  ball 
leaving  our  plant  and  to  this  end  extensive  microscopic  examinations  are  regularly 
made.  The  constancy  and  effect  of  the  many  abrasive  materials  used  are  kept  under 
rigid  control. 

Microphotographs  1,  2,  3  and  4  show  the  highly  magnified  surfaces  of  several 
makes  of  balls  for  comparison. 

No.  1  shows  the  Hoover  standard. 

At  the  top  of  this  page  is  shown  the  apparatus  on  which  microscopic  examinations 
and  photographs  are  made. 


80 


CHEMICAL 
LABORATORY 

WE  HAVE  an  up-to-date  Chemical  Laboratory  which  co- 
operates with  the  Metallurgical  Department  in  the 
control  of  the  raw  material  which  is  used  in  the  pro- 
duction of  the  Hoover  Steel  Balls,  as  well  as  the  solution  of  the 
different  problems  which  are  constantly  arising  in  a  plant  that  is 
aiming  to  produce  a  product  as  near  perfect  as  scientific  methods 
and  human  efficiency  can  make  it. 

Drillings,  and  in  some  cases  millings,  are  taken  from  the 
samples  which  are  brought  to  the  Metallurgical  Department 
from  each  shipment  of  steel  which  is  received  at  the  plant, 
whether  for  the  production  of  balls  or  to  be  used  for  the  produc- 
tion of  machine  parts  that  may  be  required  in  the  plant.  These 
drillings,  or  millings,  as  the  case  may  be,  are  analyzed  in  the 
Laboratory.  The  percentage  of  carbon,  manganese,  phosphorus, 
sulphur  and  chromium  is  determined  in  all  steel  used  for  the 
production  of  balls.  In  the  case  of  Header  Die  Steel,  which  is 
used  to  make  the  dies  that  forge  the  balls,  the  percentage  of 
carbon  is  determined  on  each  bar,  and  if  it  should  be  an  alloy 
steel  other  elements  are  determined,  and  a  complete  analysis 
is  made  on  one  sample  taken  from  the  shipment. 

Samples  are  also  taken  from  each  shipment  of  Brass  and 
Bronze  Wire  or  Rod,  which  is  received  at  the  plant,  and  from 
which  are  made  our  Brass  and  Bronze  Balls.  These  are  analyzed 
to  determine  the  quantities  of  tin,  lead,  copper,  iron,  zinc,  and 
also  any  elements  that  might  have  an  injurious  effect  on  the 
service  rendered  by  the  finished  balls.  As  the  composition  in 
a  great  measure  controls  the  hardness,  resistance  to  abrasion, 
resistance  to  corrosion,  and  therefore  the  life  of  the  finished  balls, 
it  can  be  seen  how  very  important  it  is  that  a  careful  analysis 
should  be  made  of  all  raw  material  from  which  these  balls  are 
produced. 

A  great  many  oils  and  greases  are  used  in  the  plant  for 
various  purposes,  and  these  must  be  all  carefully  tested  and 
graded.  For  instance,  the  finished  balls  are  packed  in  a  mixture 
of  an  oil  and  a  grease  and  it  is  very  important  that  these  should 
be  absolutely  free  from  any  element  such  as  acids,  sulphides  or 
water,  as  any  of  these  would  etch  and  oxidize  the  surface  of  the 


81 


balls  in  a  short  time  so  that  they  would  be  rendered  useless  for 
our  customers.  The  same  thing  applies  to  the  paper  used  in 
lining  the  boxes  in  which  the  balls  are  packed  for  shipment.  The 
leather  used  to  put  the  final  polish  on  the  balls  must  also  be  free 
from  acid  and  moisture,  or  they  would  be  rejected  by  the  Inspec- 
tion Department  on  account  of  rust  spots.  A  surface  so  highly 
finished  is  very  sensitive  and  must  be  carefully  protected  not 
only  during  production  but  in  the  packing,  and  this  is  the  reason 
the  surface  of  the  balls  is  so  carefully  covered  with  oil  to  prevent 
even  the  atmospheric  moisture  affecting  them. 

Fuels  in  the  form  of  coal,  oil  and  gas  are  also  graded  and 
combustion  problems  investigated  in  this  department.  The  effect 
on  the  finished  product  of  the  different  modes  of  handling  the 
balls  during  production  must  be  considered,  and  even  the  humi- 
dity of  the  room  in  which  they  are  inspected  has  to  be  reckoned 
with.  It  can,  therefore,  be  seen  that  besides  the  routine  control 
of  raw  material,  etc.,  a  number  of  interesting  questions  arise 
from  time  to  time  which  the  Chemical  Laboratory  must  assist 
in  solving. 


*    £« 

«      gS 

S-2 
•c     e,sc 

g  °° 
s  l: 

a  •£» 

S     B  te 


II 


•s  •?§ 
S   g! 

^          C    o, 


c  o^S  e  e 


84 


I: 

li 


if 

•*•» 

I* 

IS 

s! 


5* 

•si 


•5! 
a 

<»>  c 


! 

Sl 


11: 

"S.B 

I  Is 


• 


86 


s 
si 


h 


I! 


ti 


87 


88 


89 


•     «e  0  fc 

a  v.  ^~ 


ill! 

5  h  *S 


«. 

1111! 


t 


il 


90 


91 


5-8 


cc  «>  0 


1 

5*1 

H* 

o  S  o 


8is& 


lol 


«  c 

§.'= 
£§ 

c-o 


S  «> 
8? 


=-  o 

I 


I! 


51 


TUMBLING  BARREL  ROOM— This  room  is  equipped  with  a  variety 
of  tumbling  barrels,  cleaning  barrels  and  rotary  kegs,  all  of  which  serve  some 
special  purpose,  depending  upon  the  size  of  ball  or  the  grade  of  finish  desired. 


94 


I? 


*!! 
Ill 


ts 

OQ  S-« 

^  c  c 


96 


97 


98 


•$•2 

""*  a> 

I! 

•?* 

•i"B 


i  c 

I! 


>  c 


100 


IS 

** 


11 


•a  h 

•80 


i] 


I! 
ft 


=» 
=  i 


l 


101 


-  * 

II 


31 


102 


i! 


103 


104 


105 


106 


107 


108 


109 


WEIGHTS  OF  STEEL  BALLS 


Diameter  of            Decimal 
Ball  (Inches)            (Inches) 

WEIGHT  PER  BALL 

Grammes 
(Metric) 

Ounces 

(Avoir) 

Pounds 

(Avoir) 

1-16                         .0625 

.0166 

.00096 

.00006 

3-32                         .09375 

.0547 

.00193 

.00012 

1-8                           .125 

.1302 

.00457 

.00029 

5-32 

.15625 

.2552 

.00898 

.00056 

3-16                         .1875                                .4408 

.01552 

.00097 

7-32                         .21875 

.6993 

.02461 

.00154 

1-4                           .25 

1.0463 

.03680 

.00230 

9-32                         .28125 

1.4865 

.05231 

.00327 

5-16                         .3125 

2.0415 

.07184 

.00449 

11-32                       .34375                           2.7141 

.09550 

.00597 

3-8 

.375                               3.5226 

.12400 

.00775 

7-16 

.4375                             5.5871 

.19722 

.01229 

1-2 

.50                                 8.3498 

.29392 

.01837 

9-16                         .5625 

11.8923 

.41856 

.02616 

5-8                           .  625 

16.2947 

.57520 

.03585 

11-16                       .6875 

21.6873 

.76336 

.04771 

3-4                           .  75 

28.1872 

.99200 

.06200 

13-16                       .8125 

35.7585 

1.25872 

.07867 

7-8 

.875 

44.7872 

1.57648 

.09853 

15-16 

.9375                           55.0169 

1.93664 

.12104 

66.8257 

2.35232 

.14702 

-1/16 

.0625                           80.1379 

2.8199 

.17626 

-1/8 

.125 

95.1271 

3.3473 

.20923 

-3/16 

.1875 

111.8809 

3.9369 

.24608 

-1/4 

.25 

130.4965 

4.5919 

.28702 

-5/16 

.3125                         151.0656 

5.3157 

.33226 

-3/8 

.375 

173.6764 

6.1113 

.38199 

-7/16 

.4375 

198.4563 

6.9833 

.43649 

-1/2 

.50 

225.4820 

7.9343 

.49594 

-9/16 

.5625 

254.8682 

8.9683 

.56057 

-5/8 

.625 

286.6917 

10.0881 

.63056 

-11/16                       .6875 

321.0544 

11.2973 

.70614 

-3/4                           .75 

358.0711 

12.5998 

.78756 

-13/16                       .8125 

397.8185 

13.9985 

.87498 

-7/8                           .875 

440.398 

15.4968 

.96864 

1-15/16                       .9375 

485.939 

17.0993 

.06880 

2 

2. 

534.491 

18.8077 

.17559 

2-1/8 

2.125 

641.101 

22.5591 

.41007 

2-1/4 

2.25 

761.019 

26.7788 

.67382 

2-3/8 

2.375 

895.037 

31.4947 

.96859 

2-1/2 

2.50 

1043.924 

36.7340 

2.29608 

2-5/8 

2.625 

1208.474 

42.5239 

2.65798 

2-3/4 

2.75    ••   «' 

1389.436 

48.8916 

3.05600 

2-7/8 

2.875 

1587.727 

55.8691 

3.49213 

3 

3. 

1803.881 

63.4751 

3.96755 

3-1/8 

3.125 

2038.920 

71.7457 

4.48451 

3-1/4 

3.25 

2293.482 

80.7033 

5.04440 

3-3/8 

3.375 

2568.460 

90.3792 

5.64920 

3-1/2 

3.50 

2864.492 

100.7960 

6.30031 

3-5/8 

3.625 

3183.875 

112.0345 

6.99997 

3-3/4 

3.75 

3523.164 

123.9734 

7.74903 

3-7/8 

3.875 

3887.462 

136.7923 

8.55028 

4 

4. 

4275.876 

150.4599 

9.40458 

4-U4 

4.25 

5128.882 

180.4756 

11.28073 

4-1/2 

4.50 

6088.179 

214.2314 

13.39065 

4-3/4 

4.75 

7160.402 

251.9608 

15.74896 

S 

5. 

8351.420 

253.4605 

18.36854 

C  =  Contents  in  Cubic  Inches. 
=  4/3  TT  R3  =  4.1888  R3  =  .5236  D3 

W  =  Weight  of  Steel  Balls  in  pounds. 

=  R3  (.28065  X  4.1888)  =  1.17558  R3  =  .14695  D 


110 


FORMULA  FOR   DETERMINING   PITCH    DIA. 

OF  BALL  CIRCLE  AND  CLEARANCE 

BETWEEN  BALLS 


Notation: 

Di  =  Pitch  Dia.  of  Ball  Circle. 

D2  =  Dia.  of  Circumscribed  Circle. 

Ds  =  Dia.  of  Inscribed  Circle. 

d  =  Dia.  of  Balls. 

N  =  Number  of  Balls  in  the  Ring. 

S  =  Clearance  Between  Each  Pair  of  Balls. 


Di  =  (d+S)XCSC. 


180  °\ 
N  / 


/ISO 


)3  =  Di-d 

/180 
=  DiXSIN.      f 


180  °\ 

IT)-' 


The  following  table  gives  the  value  of  the  CSC.  and  SIN.  for  "N"  Balls. 


No.  of  Balls 

"N" 

Angle  a 
180° 

CSC. 
180° 

SIN. 
180° 

N 

N 

N 

6 

30° 

2.00000 

.50000 

7 

25°—  42'—  51.43" 

2.30476 

.43388 

8 

22°—  30' 

2.61313 

.38268 

9 

20° 

2.92381 

.34202 

10 

18° 

3.23607 

.  30902 

11 

16°—  21'—  49.09" 

3.54947 

.28173 

12 

15° 

3.86370 

.25882 

13 

13°—  50'—  46.16" 

4.17858 

.23932 

14        12°  —  51'—  25.72" 

4.49396 

.22252 

15        12° 

4.80973 

.20791 

16 

11°—  15' 

5.12583 

.  19509 

17        10°—  35'—  17.65" 

5.44219 

.  18375 

18         10° 

5.75877 

.  17365 

19         9°—  28'—  25.26" 

6.07554 

.  16459 

20         9° 

6.39247 

.15643 

21         8°—  34'—  17.14" 

6.70950 

.  14904 

22         8°  —  10'  —  54.55" 

7.02667 

.14231 

23         7°  —  49'  —  33.91" 

7.34394 

.13617 

24         7°—  30' 

7.66130 

.13053 

25         7°—  12' 

7.97873 

.12533 

26 

6°—  55'—  23.08" 

8.29623 

.12054 

27 

6°—  40' 

8.61380 

.11609 

28 

6°—  25'—  42.86" 

8.93140 

.11196 

29 

6°—  12'—  24.82" 

9.24907 

.10812 

30 

6° 

9.56677 

.  10453 

111 


THE  CIRCLE 


d  =  Diameter  of  Circle. 

C  =  Circumference  of  Circle. 

C=7rd  =3.141593  d 


A  =  Area  of  Plane  Surface. 
7r  =  3.141593 

Trd2 

A  = =  .785398  d2 

4 


Areas  of  Circles  are  to  Each  other  as  the  Squares  of  their  Diameters. 
THE  SPHERE 

V  =  Volume  of  Sphere. 


d  =  Diameter  of  Sphere. 

S  =  Area  of  Convex  Surface. 

d2 


V 


.523599  d3 


Surfaces  of  Spheres  are  to  each  other  as  the  Squires  of  their  Diameters. 
The  Volume  of  a  Shpere  =  2/3  the  Volume  of  its  Circumscribing  Cylinder. 
Volumes  of  Spheres  are  to  each  other  as  the  Cubes  of  their  Diameters. 


BALL  DIA. 
IN  INCHES 

C  RCUM. 
N  INCHES 

AREA 

VOLUME 
CU.-  INCHES 

SECTION 
SQ.  INCHES 

CONVEX  SURFACE 
SQ.  INCHES 

/SZ 

.09818 

.00077 

.00307 

.00002 

/16 

.  19635 

.00307 

.01227 

.00013 

/SZ 

.29452 

.00690 

.02761 

.  00043 

/8 

.  39270 

01227 

.04909 

.00102 

/SZ 

.49087 

.01917 

.  07670 

.00200 

/16 

.  58905 

.02761 

.11045 

.00345 

/32 

.68722 

.  03758 

.  15033 

.  00548 

/4 

.78540 

.04909 

.19635 

.00818 

/32 

.88357 

.06213 

.24851 

.01165 

16 

.98175 

.07670 

.  30680 

.01598 

11  32 

1.0799 

.09281 

.37123 

.02127 

3  8 

.1781 

.11045 

.44179 

.  02761 

IS  SZ 

.2763 

.  12962 

.51848 

.03511 

7  16 

.3744 

.15033 

.60132 

.04385 

15  32 

.4726 

.  17257 

.  05393 

1  Z 

.5708 

.19635 

.78540 

.  06545 

9  16 

.7671 

.24850 

.  99403 

.09319 

5  8 

.9635 

.30680 

.2272 

.12783 

11  16 

.1598 

37122 

.4849 

.17014 

S  4 

.3562 

.44179 

.7671 

.  22089 

.5525 

.51849 

.0739 

.  28084 

7/8 

.7489 

.60132 

.4053 

.35077 

15/16 

.9452 

.69029 

.7611 

.43143 

1. 

.1416 

.7854 

.1416 

.52360 

1/16 

.3379 

.8866 

.5466 

.  62804 

1/8 

.5343 

.9940 

.9761 

.74551 

3/16 

.7306 

.107J 

.4301 

.87681 

I/* 

,- 

.9270 

.2272 

.9088 

.0227 

.1233 

.3530 

.4119 

.1839 

3/8 

.3197 

.4849 

.9396 

.3611 

7/16 

.5160 

.6230 

.4919 

.5553 

1/Z 

.7124 

.7671 

.0686 

.7671 

/16. 

.9087 

.9175 

.6699 

.9974 

/8 

.1051 

.0739 

.2957 

.2468 

1  /16 

.3014 

.2365 

.9461 

/4 

.4978 

.4053 

.6211 

.8062 

1  /16 

.6941 

.5802 

1 

.321 

.1177 

/8 

.8905 

.7612 

.044 

.4514 

1  /16 

.0868 

.9483 

1 

.793 

.8083 

2. 

.2832 

.1416 

1 

.566 

.1888 

/16 

.4795 

.3410 

1 

.364 

.5939 

.6759 

.5466 

.186 

.0243 

/16 

.8722 

7583 

1 

.033 

.4809 

/4 

.0686 

.9761 

.904 

.9641 

/16 

.2649 

.2000 

1 

.800 

.4751 

n 

.4613 

.4301 

.7Z1 

.0144 

/16 

.6576 

.6664 

1 

.666 

.5829 

/Z 

.8540 

.9087 

1 

.635 

.1813 

/16 

.0503 

.1572 

20  629 

.8103 

/8 

.2467 

.4119                     21.648 

.4708 

1  /16 

.4430 

.6727                     22.691 

1 

.164 

It 

.6394 

.9396 

23.758 

1 

.889 

I  /16 

.8357 

.2126 

24.850 

1 

.649 

/8 

.0321 

.4918 

25.967 

1 

.443 

1  /16 

.2484 

.7771 

27.109 

1 

.272 

3 

.4248 

.0686 

28.274 

| 

.137 

1/16 

6211 

3662 

29.465 

1 

1/8 

.8175 

.6699 

30.680 

I 

'979 

3/16 

.014 

.9798 

31.919 

.957 

1/4 

.210 

.2958 

33.183 

] 

974 

i/l« 

.407 

.6179 

34.472 

I 

.031 

S/8 

.60S 

.9462 

35.784 

20.129 

7/16 

.799 

.2806 

37.122 

21  .  268 

1/Z 

.996 

.6211 

38.484 

22.449 

.192 

.9678 

S9.872 

23.674 

.388 

.321 

41.283 

24.942 

11/16 

.585 

.680 

42.719 

26.254 

3/4 

.781 

44.179 

27.611 

13/16 

977 

.tit 

45  .  664 

29.016 

7/8 

174 

.798 

47.173 

SO  466 

15/16 

.370 

48.708 

3  .965 

4. 

12.566 

12  566 

50.465 

33.510 

112 


DECIMAL  EQUIVALENTS  OF  FRACTIONS 
OF  AN  INCH 


Fract. 

Dec. 

Fract. 

Dec. 

Fract. 

Dec. 

Fract. 

Dec. 

1 

17 

33 

49 

— 

.015625 

— 

.  265625 

— 

.515625 

— 

.765625 

64 

64 

64 

64 

I 

9 

17 

25 

— 

.03125 

— 

.28125 

— 

.53125 

— 

.78125 

32 

32 

32 

32 

3 

19 

35 

51 

— 

.046875 

— 

.296875 

— 

.546875 

— 

.796875 

64 

64 

64 

64 

1 

5 

9 

13 

_ 

.0625 

__ 

.3125 

_ 

.5625          — 

.8125 

16 

16 

16 

16 

5 

21 

1  37 

i  53 

mm 

.078125 

_ 

.328125   — 

.578125  !  — 

.828125 

64 

64 

!  64 

!  64 

3 

11 

19 

27 

__ 

.09375 

•H 

.34375 

.59375      — 

.84375 

32 

32 

. 

32 

32 

7 

23 

39 

55 

— 

.  109575 

— 

.359375 

.609375 

— 

.859375 

64 

64 

64 

64 

1 

3 

5 

7 

.125 

.375 

.625 

.875 

8 

8 

.• 

8 

8 

9 

25 

41 

57 

_ 

.  140625 

_ 

.  390625 

.640625 

_ 

.890625 

64 

64 

64 

64 

5 

13 

21 

29 

__ 

.  15625 

_ 

.40625 

_ 

.65625 

__ 

.  90625 

32 

32 

32 

32 

11 

27 

43 

59 

— 

.171875 

— 

421875 

.671875 

— 

.921875 

64 

64 

64 

64 

3 

7 

11 

15 

— 

.1875 

— 

.4375 

.6875 

— 

.9375 

16 

16 

16 

16 

13 

29 

45 

61 

_ 

.203125 

__ 

.453125 

__ 

.703125 

_ 

.953125 

64 

64 

64 

64 

7 

15 

23 

31 

__ 

.21875 

_ 

.46875 

_ 

.71875 

_ 

.96875 

32 

32 

32 

32 

15 

31 

47 

63 

— 

.234375 

_ 

.484375 

_ 

.734375 

_ 

.984375 

64 

64 

64 

64 

1 

1 

3 

— 

.25 

5 

.75 

1 

4 

2 

4 

TABLE  OF  DECIMAL  EQUIVALENTS  OF  MILLI- 
METERS   AND  FRACTIONS    OF    MILLIMETERS 


1/100  mm.  =  .0003937". 


mm.  Inches  mm.  Inches  mm.  Inches       |      mm.  Inches  mm.  Inches 


1/50  =  .00079 

"/50  =  .00866 

21/50=  .01654 

31/50=  .02441 

41/50=  .03228 

2/50=  .00157 

i«/50  =  .00945 

22/50  =.01732 

3*/50  =  .  02520 

42/50  =.03307 

3/50=  .00236 

13/50  =.01024 

23/50=.  01811 

33/so  =.02598 

43/50  =  .  03386 

4/50  =.003  15 

14/50  =  .01102 

24/5o=  .01890 

34/50  =  .  02677 

44/so  =  .  03465 

5/50=.  00394 

15/50=.  01181 

25/50=  .01969 

35/50  =  .  02756 

45/50=  .03543 

6/50  =.00472 

16/50  =  .01260 

26/50=  .02047 

36/50  =.02835 

46/5o  =.03622 

,     7/50=  .  00551 

17/50=  .01339 

27/50=  .02126 

37/50=  .02913 

47/50=  .03701 

8/50  =  .  00630 

18/50  =.01417 

28/50  =  .  02205 

38/M>=.  02992 

48/so  =.03780 

9/50=  .00709 

19/50=  .01496 

29/50=  .02283 

29/50=  .03071 

49/50  =  .  03858 

I0/5o=  .00787 

S°/50=  .01575 

so/so  =.02362 

40/50=  .03150 

10      mm.  =  l  Centimeter  =   0.3937  inches 

10      cm.  =1   Decimeter   =   3.937  inches 

10      dm.  =1   Meter  =39.37  inches 

25. 4  mm.  =  1  English   Inch. 


113 


CONVERSION   TABLE 

DECIMAL  EQUIVALENTS  OF  MILLIMETERS  IN  INCHES 

1  m/m  to  500  m/m. 
1  m/m  =  .03937027" 


nun. 

Inches 

m.m. 

Inches 

m.m. 

Inches 

m.m 

Inches 

m.m 

Inches 

man 

Inches 

m.m 

Inches 

] 

.03937027 

7ft 

2.87402971 

145 

5.70868915 

eii 

8.50397832 

287 

11  .29926749 

358 

14.09455666 

429 

16.88954583 

2 

.07874054 

74 

2.91339998 

14(i 

5.74805942 

217 

8.54334859 

•288 

11  .33863776 

359 

14.13392693 

430 

16.92921610 

3 

.11811081 

7* 

2.95277025 

147 

5.78742969 

-218 

8.58271886 

289 

11  37800803 

300 

14.17329720 

431 

16.96858637 

.15748108 

7(i 

2.99214052 

14S 

5.82679996 

-219 

8.62208913 

291 

11  41737830 

301 

14.21266747 

432 

17  00795664 

.19685135 

77 

3  03151079 

149 

5.86617023 

221 

8.66145940 

-291 

11.45674857 

302 

14.25203774 

433 

17.04732691 

.23622162 

78 

3.07088106 

150 

5.90554050 

-2-21 

8  70082967 

292 

11.49611884 

563 

14  29140801 

434 

17.08669718 

.27559189 

79 

3.11025133 

151 

5.94491077 

•2-2-2 

8.74019994 

•2!)3 

11  53548911 

304 

14.33077828 

435 

17  12606745 

.31496216 

80 

3.14962160 

152 

5.98428104 

•2-23 

8.77957021 

•2!)  4 

1  1  .  57485938 

505 

14.37014855 

430 

17.16543772 

.35433243 

81 

3  18899187 

153 

6.02365131 

-2-24 

8.81894048 

•2!)5 

11  61422965 

500 

14  40951882 

437 

17  20480799 

10 

.39370270 

82 

3  22836214 

154 

6.06302158 

-2-2.-, 

8  85831075 

296 

1  1  65359992 

507 

14.44888909 

438 

17.24417826 

11 

.  43307297 

88 

3.26773241 

1  55 

6  10239185 

22  (i 

8.89768102 

•297 

11.69297019 

568 

14.48825936 

439 

17.28354853 

18 

.47244324 

84 

3.307102C8 

156 

6.14176212 

-227 

8  93705129 

298 

11  73234046 

309 

14.52762963 

440 

17.32291880 

19 

.51181351 

85 

3.34647295 

157 

0.18113239 

•2-2S 

8.97642156 

2!)!) 

11  77171073 

370 

14.56699990 

441 

7.36228907 

14 

.55118378 

86 

3.38584322 

15S 

6.22050266 

22!) 

9.01579183 

Kin 

11.81108100 

571 

14.60637017 

44-2 

17  40165934 

1.5 

.59055405 

87 

3  42521349 

159 

6.25987293 

230 

9.05516210 

301 

11  85045127 

37-2 

14.64574044 

443 

7.44102961 

10 

.  62992432 

88 

3.46458376 

160 

6.29924320 

-231 

9  09453237 

i()-2 

11.88982154 

373 

14.68511071 

444 

17.48039988 

17 

.66929459 

89 

3.50395403 

K.I 

6  33861347 

-2:!  2 

9.13390264 

503 

11  92919181 

574 

14.72448098 

145 

17.51977015 

IS 

.70866486 

90 

.54332430 

162 

6.37798374 

2:!:! 

9  17327291 

504 

1  1  .  96856208 

575 

14.76385125 

440 

7.55914042 

1!) 

.74803513 

91 

.58269457 

1  63 

6  41735401 

234 

9  21264318 

505 

12.00793235 

570 

14.80322152 

447 

7.59851069 

20 

.78740540 

98 

.  C2206484 

K!4 

6.45672428 

235 

9  25201345 

500 

12.04730262 

377 

14.84259179 

44S 

7.63788096 

21 

.82677567 

93 

.66143511 

Ki5 

6.49609455 

230 

9.29138372 

507 

12.08667289 

!78 

14.88196206 

149 

7.67725123 

2-2 

.86614594 

94 

.  70080538 

100 

6.53546482 

-237 

9  .  33075399 

ios 

12  12604316 

379 

14.92133233 

150 

7.71662150 

*S 

.90551621 

95 

.74017565 

107 

6.57483509 

238 

9  37012426 

!()!) 

12  16541343 

580 

14.96070200 

451 

7.75599177 

•24 

.94488648 

!>o 

.  77954592 

168 

6.61420536 

23!) 

9  40949453 

510 

12.20478370 

581 

15.00007287 

452 

7.79536204 

«5 

.98425675 

97 

.81891619 

169 

6  65357563 

240 

9.44886480 

ill 

12.24415397 

iS  -2 

15.03944314 

153 

7.83473231 

20 

.02362702 

98 

.  85828646 

170 

6  69294590 

241 

9  .  48823507 

312 

12  28352424 

383 

15.07881341 

454 

7.87410258 

87 

.  06299729 

!»!» 

.89765673 

171 

6  73231617 

21-2 

9  52760534 

313[12  32289451 

384 

15.11818368 

155 

7.91347285 

88 

.  10236756 

100 

93702700 

17-2 

6.77168644 

243 

9.56697561 

314  12.36226478 

585 

15.15755398 

450 

7.95284312 

*9 

.14173783 

101 

.97639727 

173 

6  81105671 

244 

9  .  60634588 

3  la!  12  40163505 

580 

15.19692422 

457 

7.99221339 

SO 

.18110810 

102 

01576754 

174 

6  85042698 

245|  9.64571615 

316|l2.  44100532 

387 

15.23629449 

158 

8  03158366 

:u 

.22047837 

103 

05513781 

175 

6.88979725 

246 

9.68508642 

517  12.48037559 

5S8 

15.27566476 

15!) 

8.07095393 

3-2 

.25984864 

104 

.  09450808 

176 

6.92916752 

247 

9.72445669 

31812.51974586 

18!) 

15  31503503 

400 

8.11032420 

33 

.29921891 

10.-, 

.13387835 

177 

6  96853779 

248 

9.76382696 

319  12.55911613 

.390 

15.35440530 

401 

8.14969447 

34 

.33858918 

100 

.17324862 

17S 

7  00790806 

249 

'9.80319723 

320  12.59848640 

5!)! 

15.39377557 

40-2 

8.18906474 

85 

.37795945 

107 

.21261889 

17!) 

7.04727833 

250 

9.84256750 

321  12.63785067 

392 

15.43314584 

403 

8.22843501 

30 

.41732972 

108 

.25198916 

ISO 

7  .  08664860 

251 

9.88193777 

322 

12.67722694 

393J  15.  4725  1611 

404 

8  .  26780528 

SI 

.  45669999 

109 

29135943 

181 

7.12601887 

252 

9  92130804 

i23 

12  71659721 

39415.51188638 

165 

8  30717555 

98 

.  49607026 

110 

.33072970 

18-2 

7.16538914 

253i  9.96067831 

i-24 

12  75596748 

595 

15.55125665 

400 

8.34654582 

39 

.53544053 

111 

.  37009997 

183 

7.20475941 

254'lO.  00004858 

525 

12  79533775 

590 

15.59062692 

407 

8  38591609 

40 

.57481080 

11-2 

40947024 

184 

7.24412968 

255 

10.03941885 

520 

12.83470802 

597 

15.62999719 

108 

8  42528636 

41 

.61418107 

11.'! 

44884051 

185 

7  .  28349995 

256 

10.07878912 

i-27 

12  87407829 

598 

15.66936746 

469 

8.46465663 

4-2 

.65355134 

114 

.48821078 

186 

7.32287022 

-257 

10.11815939 

•528 

12  91344856 

i!)!) 

15  70873773 

470 

18  50402690 

43 

.69292161 

115 

52758105 

187 

7.36224049 

258 

10  15752966 

529 

12.95281883 

400 

15  74810800 

471 

18.54339717 

44 

.7?229188 

116 

56695132 

188 

7.40161076 

2;,i) 

10  19689993 

;:!(i 

12  99218910 

401 

15.78747827 

47-2 

8.58276744 

4.) 

.77166215 

117 

.60632159 

18!) 

7.44098103 

-2(10 

10  23627020 

!31 

13  03155937 

40-2 

15.82684854 

473 

18.62213771 

4(i 

.81103242 

US 

.64569186 

190 

7.48035130 

-261 

10  27564047 

532 

1  3  07092964 

403 

15.86621881 

474 

18.66150798 

47 

.85040269 

11!) 

68506213 

11)1 

7.51972157 

•262 

10  31501074 

133 

13.11029991 

404 

15.90558908 

475 

18.70087825 

48 

.88977296 

120 

72443240 

192 

7.55909184 

203 

10.35438101 

•534 

13  14967018 

105 

15  94495935 

470 

8  74024852 

4!) 
50 

.92914323 
.96851350 

121 
122 

.  76380267 
.80317294 

193 
1!)4 

7  59846211 
7.63783238 

201 
-265 

10  39375128 
10  43312155 

i:i.-, 

530 

13  18904045 
13.22841072 

407 

15  98432962 
16.02369989 

477 
478 

8  77961879 
8  81898906 

51 

00788377 

123 

.84254321 

195 

7  67720265 

200 

10.47249182 

537 

13  26778099 

408 

16.06307016 

479 

8  85835933 

52 

.04725404 

124 

.88191348 

196 

7  71657292 

•207 

10  51186209 

i:is 

13  30715126 

40!) 

16.  10244043 

480 

8  89772960 

53 

.08662431 

1-25 

92128375 

197 

7.75594319 

20S 

10  55123236 

i:59 

13.34652153 

410 

16  14181070 

481 

8.93709987 

,U 

.12599458 

126 

.  96065402 

IDS 

7.79531346 

•26!) 

10.59060203 

540 

13  38589180 

411 

16.18118097 

48-2 

8.97647014 

55 

.16536485 

127 

.  00002429 

HI!) 

7  .  83468373 

•270 

10.62997290 

341 

13  42526207 

41'2 

16  22055124 

483 

9  01584041 

56 

.20473512 

1-2S 

.  03939456 

-200 

7.87405400 

•271 

10.66934317 

54-2 

13  46463234 

413 

16.25992151 

484 

9  05521068 

57 

24410539 

129 

.07876483 

-201 

7.91342427 

•27-2 

10.70871344 

343 

13  50400261 

414 

16.29929178 

485 

9  09458095 

58 

.28347566 

130 

.11813510 

-20-2 

7.95279454 

273 

10.74808371 

•544 

13  54337288 

415 

16.33866205 

480 

9  13395122 

53 

.32284593 

131 

.  15750537 

•20:! 

7.99216481 

•274 

10.78745398 

545 

13.58274315 

410 

16.37803232 

487 

9  17332149 

(i() 

.36221620 

132 

.19687561 

-204 

8.03153508 

•275 

10.82682425 

340 

13  62211342 

417 

16  41740259 

488 

9  21269176 

61 

.40158647 

133 

23624591 

205 

8  .  07090535 

•27  (i 

10  86619452 

547 

13  66148369 

4  IS 

16.45677286 

48!) 

9  25206203 

62 

44095674  .134 

.27561618 

206 

8  11027562277 

10  90556479 

348 

13.70085396 

419 

16  49614313 

490 

9  29143230 

03 

.48032701  135 

31498645 

•207 

8  14964589 

•278 

10.94493506 

549 

13  74022423 

420 

16  53551340 

491 

19  33080257 

04 

.51969728 

136 

35435672  208 

8.18901616 

279 

10.98430533 

550 

13  77959450 

421  16  57488367 

492 

19.37017^54 

65 

55906755 

137 

.39372699209 

8.22838643 

•280 

11.02367560 

351 

13.81896477 

422  16  61425394 

493 

19  40954311 

6(i 

.59843782 

138 

43309726  210 

8.26775670 

281 

11.06304587 

552 

13.85833504 

42316.65362421 

494 

19.44891338 

67 

68 

.63780809  139 
.67717836:140 

47246753211 
.51183780212 

8.30712697 
8.34649724 

•282 
2  S3 

11  10241614 
11  14178641 

553 
•554 

13  89770531 
13  93707558 

424'ie.  69299448 
425  16  73236475 

495 
496 

19  48828365 
19.52765392 

69 

71654863!l41 

.55120807213 

8  38586751,284 

11.18115668 

555 

13  97644585 

426 

16.77173502 

497 

19.56702419 

70 

.75591890142 

59057834214 

8.42523778  285 

11.22052695 

550 

14.01581612 

4-27 

16.81110529 

498 

19  60639446 

71 

79528917  143 

62994861 

•215 

8.46460805286 

11.25989722 

357 

14  05518639 

428 

16.85047556 

491) 

19.64576473 

72 

.83465914  144 

66931888 

500 

19.68513500 

114 


CONVERSION  TABLE 

MILLIMETER  EQUIVALENTS  OF  FRACTIONAL  INCHES 
&  inch  to  12%  Inches 


1* 

2* 

3' 

4* 

5" 

6"             7' 

8' 

9* 

10'           11' 

12' 

1 

25  3995 

50.7990 

76.1986 

101.598 

126.998 

152.397ll77.797 

203.196 

228.596 

253.995279.394 

304.794 

1/64    0.3968 

25.7964 

51    1959 

76.5954 

101.995 

127.394 

152.794178.193 

203.593 

228.992 

254.392279.791 

305.191 

1/32   0.7937 

26.1932 

51.5928 

76.9923 

102.391 

127.791 

153.190178.590 

203.990 

229.389 

254.  7891280.188 

305.588 

3/64J      .1906 

26  5901 

51.9896 

77.3892 

102.788 

128.188 

153.588178.987 

204.386 

229  .  786 

255s  1861280.  585 

306.985 

1/161      .5874 

26  9870 

52.3865 

77.7860 

103.185 

128.585 

153.984J179.384 

204  .  783 

230.183 

255.  5821280.  982 

306.381 

5/64      .9843 

27  3838 

52.7834 

78.1829 

103.582 

128.982 

154.381179.781 

205.180 

230.580 

255.  9791281.  379 

306.778 

3/32'       3812 

27.7807 

53   1802 

78.5798 

103.979 

129.378 

154.778180.177 

205.577 

230.977 

256.376^281.776 

307.175 

7  /64        7780 

28.1776 

53.5771 

78.9766 

104.376 

129.775 

155.175180.574 

205.974 

231.373 

256.773i282.173 

307.572 

1/8        .1749 

28.5744 

53.9740 

79.3735 

104.773 

130.172 

155.572  180.971 

206.370 

231.770 

257.170;282.569 

307.969 

9/64      .5718 

28  9713 

54.3708 

79.7704 

105.169 

130.569 

155.969181.368 

206.768 

232.167 

257.567,282.966 

308.366 

5/32        9686 

29  3682 

54.7677 

80.1672 

105.566 

130.966 

156.  365181.  765 

207.164 

232.564 

257.  964(283.  363 

308.763 

11/64      .3655 

29.7650 

55.1646 

80.5641 

105.963 

131.363 

156.  762182.  162 

207.561 

232.961 

258.  360^283.  760 

309.160 

3/16      .7624 

30.1619 

55.5614 

80.9610 

106.360 

131.760 

157.159  182.559 

207.958 

233.358 

258.757J284.157 

309.556 

13/64        1592 

30.5588 

55.9583 

81.3579 

106.757 

132.156 

157.556182.956 

208.355 

233.755 

259.  154(284.  554 

309.953 

7/32      .5561 
15/64      .9530 
1/4  !      .3498 
17/64      .7467 

30.9556 
31.3525 
31.7494 
32.1462 

56.3552 
56.7520 
57.1489 
57.5458 

81.7547 
82.1516 
82.5485 
82.9453 

107.154 
107.551 
107.948 
108.344 

132.553 
182.950 
133.347 
133.744 

157.  953  183.  3521208.  752 
158.  350183.  749  209.  149 
158.747184.146209.546 
159.143  184.543209.943 

234.152259.551284.951 
234.  5481259.  948'285.  347 
234.  9451260.  3451285.  744 
235  .  342!260  .  742  286  .  141 

310.350 
310.747 
311.144 
311.541 

9/32J      .1436 

32.5431 

57.9426 

83.3422 

108.741 

134.141 

159.  540(184.  940 

210.339 

235.739 

261.139:286.538 

311.938 

19/64      .5404 

32  9400 

58.3395 

83.7391 

109.138 

134.538 

159.937185.337 

210.736 

236.136 

261.535'286.935 

312.334 

5/16    7.9373 

33.3368 

58.7364 

84.1359 

109.535 

134.935 

160.334  185.734 

211.133 

236.532 

261.9321287.332 

312.731 

21/641  8  3342 

33.7337 

59.1333 

84.5328 

109.932 

135.331 

160.731  186.131 

211.530 

236.930 

262.329287.729 

313.128 

11/32;  8.7310 

34.1306 

59.5301 

84.9297 

110.329 

135.728 

161.128186.527 

211.927 

237.326 

262.726!288.126 

313.525 

23/64-  9.  1279 

34  .  5274 

59.9270 

85.3265 

110.726 

136.125 

161.525186.924 

212.324 

237.723 

263.  123^288.  522 

313.922 

3/8      9  5248 

34  9243 

60  3239 

85.7234 

111.122 

136.522 

161.922187.321 

212.721 

238.120 

263.520288.919 

314.319 

25/641  9.9216 
13/3210  3185 

35.3212 
35.7180 

60.7207 
61.1176 

86.1203 
86.5171 

111.529 
111.916 

136.919 
137.316 

162.318  187.718213.118 
162.715188.115|213.514 

238.517263.9171289.316 
238.  914  264.  3131289.  713 

314.716 
315.113 

27/6410.7154 

36.1149 

61.5145 

86.9140 

112.313 

137.713 

163.112;188.512 

213.911 

239.311 

264.710290.110 

315.509 

7/1611.1122 

36.5118 

61.9113 

87.3109 

112.710 

138.109 

163.509188.909 

214.308 

239.708 

265.107290.507 

315.906 

29/6411.5091 

36.9087 

62.3082 

87.7077 

113.107 

138.506 

163.906189.305 

214.705 

240.105 

265.504'290.903 

316.303 

15/32H1.9060 

37.3055 

62.7051 

88.1046 

113.504 

138.903 

164.303189.702 

215.102 

240.501 

265.  901  j29  1.300 

316.700 

31/6412.3029 

37.7024 

63.1019 

88.5015 

113.901 

139.300 

164.700190.099 

215.499 

240.898 

266.298i291.697 

317.097 

1/2    12.6997 

38.0993 

63.4988 

88.8983 

114.297 

139.697 

165.097190.496 

215.896 

241.295 

266.695,292.094 

317.494 

33/6413.0966 

38.4551 

63.8957 

89.2952 

114.694 

140.094 

165.493190.893 

216.292 

241.692 

267.092292.491 

317.891 

17/3213.4934 

38.8930 

64.2925 

89.6921 

115.091 

140.491 

165.890191.290 

216.689 

242.089 

267.488j292.888 

318.287 

35/6413.8903 

39.2899 

64.6894 

90.0989 

115.489 

140.888 

166.287191.687 

217.086 

242.486 

267.885293.285 

318.684 

9/1614.2872 

39.6867 

65.0863 

90.4858 

115.885 

141.284 

166.684192.084 

217.483 

2-I2.SS3 

268.  282:293.  682 

319.081 

37/6414.6841 

40.0836 

65.4831 

90.8827 

116.282 

141.681 

167.081192.480 

217.880 

243.279 

268.679294.079 

319.478 

19/3215.0809 

40.4805 

65  .  8800 

91.2795 

116.679 

142.078 

167.478192.877 

218.277 

243.676 

269.076294.475 

319.875 

39/6415.4778 

40.8773 

66.2769 

91.6764 

117.075 

142.475 

167.875il93.274 

218.674 

244.073 

269.473,294.872 

320.272 

5/8  115.8747 

41.2742 

66.6737 

92.0733 

117.472 

142.872 

168.271193.671 

219.071 

244.470 

269.870295.269 

320.669 

41/6416.2715 

41.6711 

•  17.070(1 

92.4701 

117.869 

143.269 

168.668194.068 

219.467 

244.867 

270.266295.666 

321.066 

21/3216.6684 

42.0679 

67.4675 

92.8670 

118.266 

143.666 

169.065194.465 

219.864 

245.263 

270.663296.063 

321.462 

43/6417.0653 

42.4648 

67.8643 

93.2639 

118.663 

144.063 

169.462194.862 

220.261 

245.661 

271.060|296.460 

321.859 

11/1617.4621 

42.8617 

68.2612 

93.6608 

119.060 

144.459 

169.859195.258 

220.658 

246.058 

271.457'296.857 

322.256 

45/6417.8590 

43.2585 

68.6581 

94.0576 

119.457 

144.856 

170.  256I195.  655 

221.055 

246.454 

271.  8541297.  253 

322.653 

23/32  18.  2559 

43.6554 

69.0549 

94.4545 

119.854 

145.253 

170.653196.052 

221.452 

246.851 

272.251297.650 

323  .  050 

47/6418.6527 

44.0523 

69.4518 

94.8513 

120.250 

145.650 

171.050196.449 

221.849 

247.248 

272.648298.047 

323.447 

3/4    19.0496 

44.4491 

69.8487 

95.2482 

120.647 

146.047 

171.446196.846 

222.245 

247.645 

273.  0451298.444 

323.844 

49/6419.4465 

44  .  8460 

70.2455 

95.6451 

121.044 

146.444 

171.843197.243 

222.642 

248.042 

273.441:298.841 

324.241 

25/3219.8433 

45.2429 

70.6424 

96.0419 

121.441 

146.841 

172.240197.640 

223.039 

248.439 

273.  8381299.  238 

324.638 

.51/5420.2402 

45.6397 

71.0393 

96.4398 

121.838 

147.237 

172.637198.037 

223.436 

248.836 

274.235i299.635 

325.035 

13/1620.6371 

46.0366 

71.4362 

96.8357 

122.235 

147.634 

173.034198.433 

223.883 

249.232 

274.632300.032 

325.431 

53/64  21.0339 

46.4335 

71.8330 

97.2326 

122.632 

148.031 

173.431  198.830 

224.230 

249.629 

275.029300.428 

325.828 

27/3221.4308 
55/6421.8277 
7/8    22.2245 

46.8303 
47.2272 
47.6241 

72.2299 
72.6267 
73.0236 

97.6294 
98.0263 
98.4232 

123.029 
123.425 
123.822 

148.428 
148.825 
149.222 

173  .  828  199  .  227  224  .  627 
174.  224  199.  624i225.  024 
174.  6211200.  021  225.  420 

250:026!275.426;366.825 
250.423,275.823,301.222 
250.820276.220:301.619 

326.225 
326.622 
327.019 

57/6422.6214 
29/3223.0183 

48.0209 
48.4178 

73.4205 
73.8173 

98.8200 
99.2169 

124.219 
124.616 

149.619 
150.016 

175.  0181200.  418J225.  817 
175.  415200.  815!226.  214 

251  .217)276  .  616;302  .  016 
251.  614  277.013;302.  413 

327.415 
327.812 

59/6423.4151 

48.8147 

74.2142 

99.6137 

125.013 

150.412 

175.8121201.211 

226.611 

252.011 

277.410!302.810 

328.209 

lD/16'23.8120 

49.2116 

74.6111 

100.011 

125.410 

150.809 

176.209201.608 

227.008 

252.407 

277.807i303.207 

328.606 

61/6424.2089 

49  .  6084 

75.0080 

100.408 

125.807 

151.206 

176.606202.005 

227.405 

252.804 

278.204303.603 

329.003 

31/3224.6057 

50  .  0053 

75.4048 

100.804 

126.203 

151.603 

177.003202.402 

227.802 

253.201 

278.601304.000 

329.400 

63/6425.0026 

50.4021 

75.8017 

101.201 

126.600 

152.000 

177.399202.799 

228.198 

253.598,278.998304.397 

329.797 

115 


DICKINSON      BROS      GRAND 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 

Return  to  desk  from  which  borrowed. 
This  book  is  DUE  on  the  last  date  stamped  below. 


3     1972* 


00 


LD  21-100m-9,'48(B399sl6)476 


72  -1  PM  4 


